diff --git a/src/ca/CASG.cpp b/src/ca/CASG.cpp
index 16573d1bc..f5cb64e0e 100644
--- a/src/ca/CASG.cpp
+++ b/src/ca/CASG.cpp
@@ -25,8 +25,6 @@
 #include "cac.h"
 #include "sgAutoPtr.h"
 
-casgRecycle::~casgRecycle () {}
-
 CASG::CASG ( epicsGuard < epicsMutex > & guard, ca_client_context & cacIn ) :
     client ( cacIn ), magic ( CASG_MAGIC )
 {
@@ -38,12 +36,13 @@ CASG::~CASG ()
 }
 
 void CASG::destructor ( 
+    CallbackGuard & cbGuard,
     epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->client.mutexRef() );
 
     if ( this->verify ( guard ) ) {
-        this->reset ( guard );
+        this->reset ( cbGuard, guard );
         this->client.uninstallCASG ( guard, *this );
         this->magic = 0;
     }
@@ -127,36 +126,37 @@ int CASG::block (
         delay = cur_time - beg_time;
     }
 
-    this->reset ( guard );
-
     return status;
 }
 
 void CASG::reset ( 
+    CallbackGuard & cbGuard,
     epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->client.mutexRef() );
-    this->destroyCompletedIO ( guard );
-    this->destroyPendingIO ( guard );
+    this->destroyCompletedIO ( cbGuard, guard );
+    this->destroyPendingIO ( cbGuard, guard );
 }
 
 // lock must be applied
 void CASG::destroyCompletedIO ( 
+    CallbackGuard & cbGuard,
     epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->client.mutexRef() );
     syncGroupNotify * pNotify;
     while ( ( pNotify = this->ioCompletedList.get () ) ) {
-        pNotify->destroy ( guard, * this );
+        pNotify->destroy ( cbGuard, guard );
     }
 }
 
 void CASG::destroyPendingIO ( 
+    CallbackGuard & cbGuard,
     epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->client.mutexRef() );
     while ( syncGroupNotify * pNotify = this->ioPendingList.first () ) {
-        pNotify->cancel ( guard );
+        pNotify->cancel ( cbGuard, guard );
         // cancel must release the guard while 
         // canceling put callbacks so we
         // must double check list membership
@@ -166,7 +166,7 @@ void CASG::destroyPendingIO (
         else {
             this->ioCompletedList.remove ( *pNotify );
         }
-        pNotify->destroy ( guard, *this );
+        pNotify->destroy ( cbGuard, guard );
     }
 }
 
@@ -201,10 +201,11 @@ void CASG::show (
 }
 
 bool CASG::ioComplete (
+    CallbackGuard & cbGuard,
     epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->client.mutexRef() );
-    this->destroyCompletedIO ( guard );
+    this->destroyCompletedIO ( cbGuard, guard );
     return this->ioPendingList.count () == 0u;
 }
 
@@ -212,9 +213,9 @@ void CASG::put ( epicsGuard < epicsMutex > & guard, chid pChan,
     unsigned type, arrayElementCount count, const void * pValue )
 {
     guard.assertIdenticalMutex ( this->client.mutexRef() );
-    sgAutoPtr < syncGroupWriteNotify > pNotify ( guard, *this, this->ioPendingList );
+    sgAutoPtr < syncGroupWriteNotify > pNotify ( guard, *this );
     pNotify = syncGroupWriteNotify::factory ( 
-        this->freeListWriteOP, *this, pChan );
+        this->freeListWriteOP, *this, & CASG :: recycleWriteNotifyIO, pChan );
     pNotify->begin ( guard, type, count, pValue );
     pNotify.release ();
 }
@@ -223,9 +224,9 @@ void CASG::get ( epicsGuard < epicsMutex > & guard, chid pChan,
                 unsigned type, arrayElementCount count, void *pValue )
 {
     guard.assertIdenticalMutex ( this->client.mutexRef() );
-    sgAutoPtr < syncGroupReadNotify > pNotify ( guard, *this, this->ioPendingList );
+    sgAutoPtr < syncGroupReadNotify > pNotify ( guard, *this );
     pNotify = syncGroupReadNotify::factory ( 
-        this->freeListReadOP, *this, pChan, pValue );
+        this->freeListReadOP, *this, & CASG :: recycleReadNotifyIO, pChan, pValue );
     pNotify->begin ( guard, type, count );
     pNotify.release ();
 }
@@ -241,20 +242,20 @@ void CASG::completionNotify (
     }
 }
 
-void CASG::recycleSyncGroupWriteNotify ( 
-    epicsGuard < epicsMutex > & guard, syncGroupWriteNotify & io )
-{
-    guard.assertIdenticalMutex ( this->client.mutexRef() );
-    this->freeListWriteOP.release ( & io );
-}
-
-void CASG::recycleSyncGroupReadNotify ( 
-    epicsGuard < epicsMutex > & guard, syncGroupReadNotify & io )
+void CASG :: recycleReadNotifyIO ( epicsGuard < epicsMutex > & guard, 
+                            syncGroupReadNotify & io )
 {
     guard.assertIdenticalMutex ( this->client.mutexRef() );
     this->freeListReadOP.release ( & io );
 }
 
+void CASG :: recycleWriteNotifyIO ( epicsGuard < epicsMutex > & guard, 
+                            syncGroupWriteNotify & io )
+{
+    guard.assertIdenticalMutex ( this->client.mutexRef() );
+    this->freeListWriteOP.release ( & io );
+}
+
 int CASG :: printFormated ( const char *pformat, ... )
 {
     va_list theArgs;
@@ -295,13 +296,6 @@ void CASG::exception (
     }
 }
 
-void * CASG::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void CASG::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/access.cpp b/src/ca/access.cpp
index 85fe2b205..74f74325a 100644
--- a/src/ca/access.cpp
+++ b/src/ca/access.cpp
@@ -376,15 +376,35 @@ int epicsShareAPI ca_create_channel (
 int epicsShareAPI ca_clear_channel ( chid pChan )
 {
     ca_client_context & cac = pChan->getClientCtx ();
-    epicsGuard < epicsMutex > guard ( cac.mutex );
-    try {
-        pChan->eliminateExcessiveSendBacklog ( guard );
+    {
+        epicsGuard < epicsMutex > guard ( cac.mutex );
+        try {
+            pChan->eliminateExcessiveSendBacklog ( guard );
+        }
+        catch ( cacChannel::notConnected & ) {
+            // intentionally ignored
+        }
     }
-    catch ( cacChannel::notConnected & ) {
-        // intentionally ignored
-    }
-    pChan->destructor ( guard );
+    if ( cac.pCallbackGuard.get() &&
+            cac.createdByThread == epicsThreadGetIdSelf () ) {
+        epicsGuard < epicsMutex > guard ( cac.mutex );
+        pChan->destructor ( *cac.pCallbackGuard.get(), guard );
     cac.oldChannelNotifyFreeList.release ( pChan );
+    }
+    else {
+        //
+        // we will definately stall out here if all of the
+        // following are true
+        //
+        // o user creates non-preemtive mode client library context
+        // o user doesnt periodically call a ca function
+        // o user calls this function from an auxiillary thread
+        //
+        CallbackGuard cbGuard ( cac.cbMutex );
+        epicsGuard < epicsMutex > guard ( cac.mutex );
+        pChan->destructor ( *cac.pCallbackGuard.get(), guard );
+        cac.oldChannelNotifyFreeList.release ( pChan );
+    }
     return ECA_NORMAL;
 }
 
@@ -433,7 +453,7 @@ chid epicsShareAPI ca_evid_to_chid ( evid pMon )
 }
 
 // extern "C"
-int epicsShareAPI ca_pend ( ca_real timeout, int early ) // X aCC 361
+int epicsShareAPI ca_pend ( ca_real timeout, int early )
 {
     if ( early ) {
         return ca_pend_io ( timeout );
@@ -516,7 +536,7 @@ int epicsShareAPI ca_flush_io ()
 /*
  *  CA_TEST_IO ()
  */
-int epicsShareAPI ca_test_io () // X aCC 361
+int epicsShareAPI ca_test_io ()
 {
     ca_client_context *pcac;
     int caStatus = fetchClientContext ( &pcac );
@@ -551,7 +571,7 @@ void epicsShareAPI ca_signal ( long ca_status, const char *message )
  * (if they call this routine again).
  */
 // extern "C"
-const char * epicsShareAPI ca_message ( long ca_status ) // X aCC 361
+const char * epicsShareAPI ca_message ( long ca_status )
 {
     unsigned msgNo = CA_EXTRACT_MSG_NO ( ca_status );
 
diff --git a/src/ca/acctst.c b/src/ca/acctst.c
index f2d102868..a01ee131d 100644
--- a/src/ca/acctst.c
+++ b/src/ca/acctst.c
@@ -13,6 +13,7 @@
  * Authors:
  * Jeff Hill
  * Murali Shankar - initial versions of verifyMultithreadSubscr
+ * Michael Abbott - initial versions of multiSubscrDestroyNoLateCallbackTest
  * 
  */
 
@@ -1328,6 +1329,158 @@ void test_sync_groups ( chid chan, unsigned interestLevel  )
     showProgressEnd ( interestLevel );
 }
 
+#define multiSubscrDestroyNoLateCallbackEventCount 500
+
+struct MultiSubscrDestroyNoLateCallbackEventData {
+    evid m_id;
+    size_t m_nCallback;
+    int m_callbackIsOk;
+    struct MultiSubscrDestroyNoLateCallbackTestData * m_pTestData;
+};
+
+struct MultiSubscrDestroyNoLateCallbackTestData {
+    const char * m_pChanName;
+    chid m_chan;
+    epicsMutexId m_mutex;
+    epicsEventId m_testDoneEvent;
+    unsigned m_interestLevel;
+    struct MultiSubscrDestroyNoLateCallbackEventData
+        m_eventData [multiSubscrDestroyNoLateCallbackEventCount];
+};
+
+static void noLateCallbackDetect ( struct event_handler_args args )
+{
+    int callbackIsOk;
+    struct MultiSubscrDestroyNoLateCallbackEventData * const pEventData = args.usr;
+    epicsMutexLockStatus lockStatus = epicsMutexLock ( pEventData->m_pTestData->m_mutex );
+    callbackIsOk = pEventData->m_callbackIsOk;
+    pEventData->m_nCallback++;
+    epicsMutexUnlock ( pEventData->m_pTestData->m_mutex );
+    verify ( lockStatus == epicsMutexLockOK );
+    verify ( callbackIsOk );
+}
+
+static void multiSubscrDestroyNoLateCallbackThread ( void * pParm ) 
+{
+    struct MultiSubscrDestroyNoLateCallbackTestData * const pTestData = 
+              ( struct MultiSubscrDestroyNoLateCallbackTestData * ) pParm;
+    unsigned i, j;
+    int status;
+
+    status = ca_context_create ( ca_enable_preemptive_callback );
+    verify ( status == ECA_NORMAL );
+
+    status = ca_create_channel ( pTestData->m_pChanName, 0, 0,
+                           CA_PRIORITY_DEFAULT, &pTestData->m_chan );
+    status = ca_pend_io ( timeoutToPendIO );
+    SEVCHK ( status, "multiSubscrDestroyLateNoCallbackTest: channel connect failed" );
+    verify ( status == ECA_NORMAL );
+
+    /*
+     * create a set of subscriptions
+     */
+    for ( i=0; i < 10000; i++ ) {
+        unsigned int priorityOfTestThread;
+        for ( j=0; j < multiSubscrDestroyNoLateCallbackEventCount; j++ ) {
+            epicsMutexLockStatus lockStatus = epicsMutexLock ( pTestData->m_mutex );
+            verify ( lockStatus == epicsMutexLockOK );
+            pTestData->m_eventData[j].m_nCallback = 0;
+            pTestData->m_eventData[j].m_callbackIsOk = TRUE;
+            pTestData->m_eventData[j].m_pTestData = pTestData;
+            epicsMutexUnlock ( pTestData->m_mutex );
+            SEVCHK ( ca_add_event ( DBR_GR_FLOAT, pTestData->m_chan, noLateCallbackDetect,
+                        &pTestData->m_eventData[j], &pTestData->m_eventData[j].m_id ) , NULL );
+        }
+        SEVCHK ( ca_flush_io(), NULL ); 
+
+        /*
+         * raise the priority of the current thread hoping to improve our 
+         * likelyhood of detecting a bug
+         */
+        priorityOfTestThread = epicsThreadGetPrioritySelf ();
+        epicsThreadSetPriority ( epicsThreadGetIdSelf(), epicsThreadPriorityHigh );
+
+
+        /*
+         * wait for the first subscription update to arrive
+         */
+        {
+            epicsMutexLockStatus lockStatus = epicsMutexLock ( pTestData->m_mutex );
+            verify ( lockStatus == epicsMutexLockOK );
+            while ( pTestData->m_eventData[0].m_nCallback == 0 ) {
+                epicsMutexUnlock ( pTestData->m_mutex );
+                epicsThreadSleep ( 50e-6 );
+                lockStatus = epicsMutexLock ( pTestData->m_mutex );
+                verify ( lockStatus == epicsMutexLockOK );
+            }
+            epicsMutexUnlock ( pTestData->m_mutex );
+        }
+        /*
+         * try to destroy all of the subscriptions at precisely the same time that
+         * their first callbacks are running
+         */
+        for ( j=0; j < multiSubscrDestroyNoLateCallbackEventCount; j++ ) {
+            SEVCHK ( ca_clear_event ( pTestData->m_eventData[j].m_id ) , NULL );
+            epicsMutexLockStatus lockStatus = epicsMutexLock ( pTestData->m_mutex );
+            verify ( lockStatus == epicsMutexLockOK );
+            pTestData->m_eventData[j].m_callbackIsOk = FALSE;
+            epicsMutexUnlock ( pTestData->m_mutex );
+        }
+        /*
+         * return to the original priority
+         */
+        epicsThreadSetPriority ( epicsThreadGetIdSelf(), priorityOfTestThread );
+
+        if ( i % 1000 == 0 ) {
+            showProgress ( pTestData->m_interestLevel );
+        }
+    }
+
+    SEVCHK ( ca_clear_channel ( pTestData->m_chan ), NULL );
+
+    ca_context_destroy ();
+
+    epicsEventSignal ( pTestData->m_testDoneEvent );
+}
+
+/*
+ * verify that, in a preemtive callback mode client, a subscription callback never 
+ * comes after the subscription is destroyed
+ */
+static void multiSubscrDestroyNoLateCallbackTest ( const char *pName, unsigned interestLevel )
+{
+    struct MultiSubscrDestroyNoLateCallbackTestData * pTestData;
+
+    showProgressBegin ( "multiSubscrDestroyNoLateCallbackTest", interestLevel );
+
+    pTestData = calloc ( 1u, sizeof ( struct MultiSubscrDestroyNoLateCallbackTestData ) );
+    verify ( pTestData );
+    pTestData->m_mutex = epicsMutexMustCreate (); 
+    pTestData->m_testDoneEvent = epicsEventMustCreate ( epicsEventEmpty );
+    pTestData->m_pChanName = pName;
+    pTestData->m_interestLevel = interestLevel;
+    epicsThreadMustCreate (
+                      "multiSubscrDestroyNoLateCallbackTest",
+                      epicsThreadPriorityLow, 
+                      epicsThreadGetStackSize ( epicsThreadStackMedium ),
+                      multiSubscrDestroyNoLateCallbackThread,
+                      pTestData );
+
+    /*
+     * wait for test to complete
+     */
+    epicsEventMustWait ( pTestData->m_testDoneEvent );
+
+    /*
+     * cleanup
+     */
+    epicsMutexDestroy ( pTestData->m_mutex );
+    epicsEventDestroy ( pTestData->m_testDoneEvent );
+    free ( pTestData );
+
+    showProgressEnd ( interestLevel );
+}
+
 /*
  * multiSubscriptionDeleteTest
  *
@@ -3263,6 +3416,11 @@ int acctst ( const char * pName, unsigned interestLevel, unsigned channelCount,
         epicsEnvSet ( "EPICS_CA_MAX_ARRAY_BYTES", tmpString ); 
     }
 
+    /*
+     * this test creates, and then destroys, a private CA context
+     */
+    multiSubscrDestroyNoLateCallbackTest ( pName, interestLevel );
+
     status = ca_context_create ( select );
     SEVCHK ( status, NULL );
 
diff --git a/src/ca/bhe.cpp b/src/ca/bhe.cpp
index 8ede482b4..d6f1796be 100644
--- a/src/ca/bhe.cpp
+++ b/src/ca/bhe.cpp
@@ -332,13 +332,6 @@ void bhe::unregisterIIU (
     }
 }
 
-void * bhe::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void bhe::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/bhe.h b/src/ca/bhe.h
index 1660e485b..4da95202a 100644
--- a/src/ca/bhe.h
+++ b/src/ca/bhe.h
@@ -87,7 +87,6 @@ private:
                      const epicsTime & currentTime );
 	bhe ( const bhe & );
 	bhe & operator = ( const bhe & );
-    void * operator new ( size_t size );
     epicsShareFunc void operator delete ( void * );
 };
 
diff --git a/src/ca/ca_client_context.cpp b/src/ca/ca_client_context.cpp
index f0d71f5b3..b8f6d9d0b 100644
--- a/src/ca/ca_client_context.cpp
+++ b/src/ca/ca_client_context.cpp
@@ -106,7 +106,7 @@ ca_client_context::ca_client_context ( bool enablePreemptiveCallback ) :
 
     {
         osiSockIoctl_t yes = true;
-        int status = socket_ioctl ( this->sock, // X aCC 392
+        int status = socket_ioctl ( this->sock,
                                     FIONBIO, & yes);
         if ( status < 0 ) {
             char sockErrBuf[64];
@@ -126,7 +126,7 @@ ca_client_context::ca_client_context ( bool enablePreemptiveCallback ) :
         memset ( (char *)&addr, 0 , sizeof ( addr ) );
         addr.ia.sin_family = AF_INET;
         addr.ia.sin_addr.s_addr = htonl ( INADDR_ANY ); 
-        addr.ia.sin_port = htons ( PORT_ANY ); // X aCC 818
+        addr.ia.sin_port = htons ( PORT_ANY );
         int status = bind (this->sock, &addr.sa, sizeof (addr) );
         if ( status < 0 ) {
             char sockErrBuf[64];
@@ -159,9 +159,9 @@ ca_client_context::ca_client_context ( bool enablePreemptiveCallback ) :
         this->localPort = htons ( tmpAddr.ia.sin_port );
     }
 
-    epics_auto_ptr < epicsGuard < epicsMutex > > pCBGuard;
+    epics_auto_ptr < CallbackGuard > pCBGuard;
     if ( ! enablePreemptiveCallback ) {
-        pCBGuard.reset ( new epicsGuard < epicsMutex > ( this->cbMutex ) );
+        pCBGuard.reset ( new CallbackGuard ( this->cbMutex ) );
     }
 
     // multiple steps ensure exception safety
@@ -277,7 +277,7 @@ int ca_client_context :: printFormated (
 }
 
 int ca_client_context :: varArgsPrintFormated ( 
-    const char *pformat, va_list args ) const // X aCC 361
+    const char *pformat, va_list args ) const
 {
     caPrintfFunc * pFunc;
     {
@@ -751,6 +751,8 @@ epicsShareFunc int epicsShareAPI ca_clear_subscription ( evid pMon )
 {
     oldChannelNotify & chan = pMon->channel ();
     ca_client_context & cac = chan.getClientCtx ();
+    // !!!! the order in which we take the mutex here prevents deadlocks
+    {
     epicsGuard < epicsMutex > guard ( cac.mutex );
     try {
         // if this stalls out on a live circuit then an exception 
@@ -761,7 +763,25 @@ epicsShareFunc int epicsShareAPI ca_clear_subscription ( evid pMon )
     catch ( cacChannel::notConnected & ) {
         // intentionally ignored
     }
-    pMon->cancel ( guard );
+    }
+    if ( cac.pCallbackGuard.get() &&
+        cac.createdByThread == epicsThreadGetIdSelf () ) {
+      epicsGuard < epicsMutex > guard ( cac.mutex );
+      pMon->cancel ( *cac.pCallbackGuard.get(), guard );
+    }
+    else {
+      //
+      // we will definately stall out here if all of the
+      // following are true
+      //
+      // o user creates non-preemtive mode client library context
+      // o user doesnt periodically call a ca function
+      // o user calls this function from an auxiillary thread
+      //
+      CallbackGuard cbGuard ( cac.cbMutex );
+      epicsGuard < epicsMutex > guard ( cac.mutex );
+      pMon->cancel ( cbGuard, guard );
+    }
     return ECA_NORMAL;
 }
 
diff --git a/src/ca/cac.cpp b/src/ca/cac.cpp
index 42a491fec..0317f2145 100644
--- a/src/ca/cac.cpp
+++ b/src/ca/cac.cpp
@@ -568,7 +568,7 @@ bool cac::findOrCreateVirtCircuit (
 }
 
 void cac::transferChanToVirtCircuit ( 
-    unsigned cid, unsigned sid, // X aCC 431
+    unsigned cid, unsigned sid,
     ca_uint16_t typeCode, arrayElementCount count, 
     unsigned minorVersionNumber, const osiSockAddr & addr,
     const epicsTime & currentTime )
@@ -711,6 +711,7 @@ netReadNotifyIO & cac::readNotifyRequest (
 }
 
 bool cac::destroyIO (
+    CallbackGuard & callbackGuard,
     epicsGuard < epicsMutex > & guard, 
     const cacChannel::ioid & idIn, nciu & chan )
 {
@@ -787,7 +788,7 @@ void cac::recycleSubscription (
 netSubscription & cac::subscriptionRequest ( 
     epicsGuard < epicsMutex > & guard, 
     nciu & chan, privateInterfaceForIO & privChan,
-    unsigned type, // X aCC 361
+    unsigned type,
     arrayElementCount nElem, unsigned mask, 
     cacStateNotify & notifyIn,
     bool chanIsInstalled )
@@ -1021,7 +1022,7 @@ bool cac::readExcep ( callbackManager &, tcpiiu &,
 }
 
 bool cac::writeExcep ( 
-    callbackManager & mgr, // X aCC 431
+    callbackManager & mgr,
     tcpiiu &, const caHdrLargeArray & hdr, 
     const char * pCtx, unsigned status )
 {
@@ -1093,7 +1094,7 @@ bool cac::exceptionRespAction ( callbackManager & cbMutexIn, tcpiiu & iiu,
 }
 
 bool cac::accessRightsRespAction (
-    callbackManager & mgr, tcpiiu &, // X aCC 431
+    callbackManager & mgr, tcpiiu &,
     const epicsTime &, const caHdrLargeArray & hdr, void * /* pMsgBody */ )
 {
     epicsGuard < epicsMutex > guard ( this->mutex );
@@ -1110,7 +1111,7 @@ bool cac::accessRightsRespAction (
 }
 
 bool cac::createChannelRespAction (
-    callbackManager & mgr, tcpiiu & iiu, // X aCC 431
+    callbackManager & mgr, tcpiiu & iiu,
     const epicsTime &, const caHdrLargeArray & hdr, void * /* pMsgBody */ )
 {
     epicsGuard < epicsMutex > guard ( this->mutex );
@@ -1157,7 +1158,7 @@ bool cac::verifyAndDisconnectChan (
 }
 
 void cac::disconnectChannel (
-        epicsGuard < epicsMutex > & cbGuard, // X aCC 431
+        epicsGuard < epicsMutex > & cbGuard,
         epicsGuard < epicsMutex > & guard, nciu & chan )
 {
     guard.assertIdenticalMutex ( this->mutex );
diff --git a/src/ca/cac.h b/src/ca/cac.h
index ae20eef27..63acccb6f 100644
--- a/src/ca/cac.h
+++ b/src/ca/cac.h
@@ -55,7 +55,7 @@ class netSubscription;
 // used to control access to cac's recycle routines which
 // should only be indirectly invoked by CAC when its lock
 // is applied
-class cacRecycle {              // X aCC 655
+class cacRecycle {
 public:
     virtual void recycleReadNotifyIO ( 
         epicsGuard < epicsMutex > &, netReadNotifyIO &io ) = 0;
@@ -155,7 +155,8 @@ public:
         unsigned type, arrayElementCount nElem, unsigned mask, 
         cacStateNotify &, bool channelIsInstalled );
     bool destroyIO (
-        epicsGuard < epicsMutex > & guard, 
+        CallbackGuard & callbackGuard,
+        epicsGuard < epicsMutex > & mutualExclusionGuard,
         const cacChannel::ioid & idIn, 
         nciu & chan );
     void disconnectAllIO ( 
@@ -167,11 +168,6 @@ public:
         epicsGuard < epicsMutex > & guard,
         const cacChannel::ioid &id, unsigned level ) const;
 
-    // sync group routines
-    CASG * lookupCASG ( epicsGuard < epicsMutex > &, unsigned id );
-    void installCASG ( epicsGuard < epicsMutex > &, CASG & );
-    void uninstallCASG ( epicsGuard < epicsMutex > &, CASG & );
-
     // exception generation
     void exception ( 
         epicsGuard < epicsMutex > & cbGuard, 
diff --git a/src/ca/cacIO.h b/src/ca/cacIO.h
index 8086f1239..dd3955737 100644
--- a/src/ca/cacIO.h
+++ b/src/ca/cacIO.h
@@ -69,7 +69,7 @@ typedef unsigned long arrayElementCount;
 
 // 1) this should not be passing caerr.h status to the exception callback
 // 2) needless-to-say the data should be passed here using the new data access API
-class epicsShareClass cacWriteNotify { // X aCC 655
+class epicsShareClass cacWriteNotify {
 public:
     virtual ~cacWriteNotify () = 0;
     virtual void completion ( epicsGuard < epicsMutex > & ) = 0;
@@ -82,7 +82,7 @@ public:
 
 // 1) this should not be passing caerr.h status to the exception callback
 // 2) needless-to-say the data should be passed here using the new data access API
-class epicsShareClass cacReadNotify { // X aCC 655
+class epicsShareClass cacReadNotify {
 public:
     virtual ~cacReadNotify () = 0;
     virtual void completion ( 
@@ -97,7 +97,7 @@ public:
 
 // 1) this should not be passing caerr.h status to the exception callback
 // 2) needless-to-say the data should be passed here using the new data access API
-class epicsShareClass cacStateNotify { // X aCC 655
+class epicsShareClass cacStateNotify {
 public:
     virtual ~cacStateNotify () = 0;
     virtual void current ( 
@@ -131,7 +131,7 @@ private:
     bool f_operatorConfirmationRequest:1;
 };
 
-class epicsShareClass cacChannelNotify { // X aCC 655
+class epicsShareClass cacChannelNotify {
 public:
     virtual ~cacChannelNotify () = 0;
     virtual void connectNotify ( epicsGuard < epicsMutex > & ) = 0;
@@ -152,6 +152,16 @@ public:
         unsigned type, arrayElementCount count ) = 0;
 };
 
+class CallbackGuard :
+    public epicsGuard < epicsMutex > {
+public:
+    CallbackGuard ( epicsMutex & mutex ) :
+        epicsGuard < epicsMutex > ( mutex ) {}
+private:
+    CallbackGuard ( const CallbackGuard & );
+    CallbackGuard & operator = ( const CallbackGuard & );
+};
+
 //
 // Notes
 // 1) This interface assumes that when a channel is deleted then all
@@ -174,6 +184,7 @@ public:
 
     cacChannel ( cacChannelNotify & );
     virtual void destroy (
+        CallbackGuard & callbackGuard,
         epicsGuard < epicsMutex > & mutualExclusionGuard ) = 0;
     cacChannelNotify & notify () const; // required ?????
     virtual unsigned getName (
@@ -207,7 +218,15 @@ public:
         epicsGuard < epicsMutex > &, unsigned type, 
         arrayElementCount count, unsigned mask, cacStateNotify &, 
         ioid * = 0 ) = 0;
+    // The primary mutex must be released when calling the user's
+    // callback, and therefore a finite interval exists when we are
+    // moving forward with the intent to call the users callback
+    // but the users IO could be deleted during this interval.
+    // To prevent the user's callback from being called after
+    // destroying his IO we must past a guard for the callback
+    // mutex here.
     virtual void ioCancel ( 
+        CallbackGuard & callbackGuard,
         epicsGuard < epicsMutex > & mutualExclusionGuard,
         const ioid & ) = 0;
     virtual void ioShow ( 
@@ -258,7 +277,7 @@ private:
 	cacChannel & operator = ( const cacChannel & );
 };
 
-class epicsShareClass cacContext { // X aCC 655
+class epicsShareClass cacContext {
 public:
     virtual ~cacContext ();
     virtual cacChannel & createChannel ( 
@@ -277,7 +296,7 @@ public:
         epicsGuard < epicsMutex > &, unsigned level ) const = 0;
 };
 
-class epicsShareClass cacContextNotify { // X aCC 655
+class epicsShareClass cacContextNotify {
 public:
     virtual ~cacContextNotify () = 0;
     virtual cacContext & createNetworkContext ( 
@@ -297,7 +316,7 @@ public:
 // **** Lock Hierarchy ****
 // callbackControl must be taken before mutualExclusion if both are held at
 // the same time
-class epicsShareClass cacService { // X aCC 655
+class epicsShareClass cacService {
 public:
     virtual ~cacService () = 0;
     virtual cacContext & contextCreate ( 
diff --git a/src/ca/casw.cpp b/src/ca/casw.cpp
index d8334b8ca..f69632c13 100644
--- a/src/ca/casw.cpp
+++ b/src/ca/casw.cpp
@@ -131,7 +131,7 @@ int main ( int argc, char ** argv )
     }
 
     osiSockIoctl_t yes = true;
-    status = socket_ioctl ( sock, FIONBIO, &yes ); // X aCC 392
+    status = socket_ioctl ( sock, FIONBIO, &yes );
     if ( status < 0 ) {
         char sockErrBuf[64];
         epicsSocketConvertErrnoToString ( 
@@ -166,7 +166,7 @@ int main ( int argc, char ** argv )
     }
 
     osiSockIoctl_t no = false;
-    status = socket_ioctl ( sock, FIONBIO, &no ); // X aCC 392
+    status = socket_ioctl ( sock, FIONBIO, &no );
     if ( status < 0 ) {
         char sockErrBuf[64];
         epicsSocketConvertErrnoToString ( 
diff --git a/src/ca/comBuf.h b/src/ca/comBuf.h
index 2f6c6faa1..59e38780b 100644
--- a/src/ca/comBuf.h
+++ b/src/ca/comBuf.h
@@ -44,7 +44,7 @@ public:
     virtual void release ( void * ) = 0; 
 };
 
-class wireSendAdapter { // X aCC 655
+class wireSendAdapter {
 public:
     virtual unsigned sendBytes ( const void * pBuf, 
         unsigned nBytesInBuf, 
@@ -65,7 +65,7 @@ struct statusWireIO {
     swioCircuitState circuitState;
 };
 
-class wireRecvAdapter { // X aCC 655
+class wireRecvAdapter {
 public:
     virtual void recvBytes ( void * pBuf, 
         unsigned nBytesInBuf, statusWireIO & ) = 0;
@@ -114,7 +114,6 @@ private:
     unsigned nextWriteIndex;
     unsigned nextReadIndex;
     epicsUInt8 buf [ comBufSize ];
-    void * operator new ( size_t size );
     void operator delete ( void * );
     template < class T >
     bool push ( const T * ); // disabled
diff --git a/src/ca/comQueRecv.cpp b/src/ca/comQueRecv.cpp
index db797fd65..88263544d 100644
--- a/src/ca/comQueRecv.cpp
+++ b/src/ca/comQueRecv.cpp
@@ -155,7 +155,7 @@ epicsUInt32 comQueRecv::multiBufferPopUInt32 ()
         unsigned byte3 = this->popUInt8();
         unsigned byte4 = this->popUInt8();
         tmp = static_cast <epicsUInt32>
-            ( ( byte1 << 24u ) | ( byte2 << 16u ) | //X aCC 392
+            ( ( byte1 << 24u ) | ( byte2 << 16u ) |
               ( byte3 << 8u ) | byte4 );
     }
     else {
diff --git a/src/ca/comQueSend.cpp b/src/ca/comQueSend.cpp
index 5ae150be2..6ed516bb3 100644
--- a/src/ca/comQueSend.cpp
+++ b/src/ca/comQueSend.cpp
@@ -368,7 +368,7 @@ void comQueSend::insertRequestWithPayLoad (
         // the above checks verify that the total size
         // is lest that 0xffffffff
         size = static_cast < ca_uint32_t > 
-            ( dbr_size_n ( dataType, nElem ) ); // X aCC 392
+            ( dbr_size_n ( dataType, nElem ) );
         payloadSize = CA_MESSAGE_ALIGN ( size );
         this->insertRequestHeader ( request, payloadSize, 
             static_cast <ca_uint16_t> ( dataType ), 
diff --git a/src/ca/disconnectGovernorTimer.cpp b/src/ca/disconnectGovernorTimer.cpp
index 755b29cb3..f1d517f07 100644
--- a/src/ca/disconnectGovernorTimer.cpp
+++ b/src/ca/disconnectGovernorTimer.cpp
@@ -65,7 +65,7 @@ void disconnectGovernorTimer::shutdown (
 }
 
 epicsTimerNotify::expireStatus disconnectGovernorTimer::expire ( 
-    const epicsTime & /* currentTime */ ) // X aCC 361
+    const epicsTime & /* currentTime */ )
 {
     epicsGuard < epicsMutex > guard ( this->mutex );
     while ( nciu * pChan = chanList.get () ) {
diff --git a/src/ca/disconnectGovernorTimer.h b/src/ca/disconnectGovernorTimer.h
index 06b8a36a8..f636d6260 100644
--- a/src/ca/disconnectGovernorTimer.h
+++ b/src/ca/disconnectGovernorTimer.h
@@ -43,7 +43,7 @@
 #include "caProto.h"
 #include "netiiu.h"
 
-class disconnectGovernorNotify { // X aCC 655
+class disconnectGovernorNotify {
 public:
     virtual ~disconnectGovernorNotify () = 0;
     virtual void govExpireNotify ( 
diff --git a/src/ca/getCallback.cpp b/src/ca/getCallback.cpp
index e95433dd5..05e654e30 100644
--- a/src/ca/getCallback.cpp
+++ b/src/ca/getCallback.cpp
@@ -90,13 +90,6 @@ void getCallback::exception (
     }
 }
 
-void * getCallback::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void getCallback::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/getCopy.cpp b/src/ca/getCopy.cpp
index 978676ef0..23a508d9a 100644
--- a/src/ca/getCopy.cpp
+++ b/src/ca/getCopy.cpp
@@ -105,13 +105,6 @@ void getCopy::show ( unsigned level ) const
     }
 }
 
-void * getCopy::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void getCopy::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/iocinf.cpp b/src/ca/iocinf.cpp
index d6fac8178..487067c00 100644
--- a/src/ca/iocinf.cpp
+++ b/src/ca/iocinf.cpp
@@ -133,7 +133,7 @@ extern "C" void epicsShareAPI removeDuplicateAddresses
 
         if ( pNode->addr.sa.sa_family == AF_INET ) {
 
-            pTmpNode = (osiSockAddrNode *) ellFirst (pDestList);    // X aCC 749
+            pTmpNode = (osiSockAddrNode *) ellFirst (pDestList);
             while ( pTmpNode ) {
                 if (pTmpNode->addr.sa.sa_family == AF_INET) {
                     if ( pNode->addr.ia.sin_addr.s_addr == pTmpNode->addr.ia.sin_addr.s_addr && 
@@ -149,7 +149,7 @@ extern "C" void epicsShareAPI removeDuplicateAddresses
                         break;
                     }
                 }
-                pTmpNode = (osiSockAddrNode *) ellNext (&pTmpNode->node); // X aCC 749
+                pTmpNode = (osiSockAddrNode *) ellNext (&pTmpNode->node);
             }
             if (pNode) {
                 ellAdd (pDestList, &pNode->node);
@@ -168,12 +168,12 @@ static void  forcePort ( ELLLIST *pList, unsigned short port )
 {
     osiSockAddrNode *pNode;
 
-    pNode  = ( osiSockAddrNode * ) ellFirst ( pList );          // X aCC 749
+    pNode  = ( osiSockAddrNode * ) ellFirst ( pList );
     while ( pNode ) {
         if ( pNode->addr.sa.sa_family == AF_INET ) {
             pNode->addr.ia.sin_port = htons ( port );
         }
-        pNode = ( osiSockAddrNode * ) ellNext ( &pNode->node ); // X aCC 749
+        pNode = ( osiSockAddrNode * ) ellNext ( &pNode->node );
     }
 }
 
@@ -192,9 +192,9 @@ extern "C" void epicsShareAPI configureChannelAccessAddressList
     /*
      * dont load the list twice
      */
-    assert ( ellCount (pList) == 0 ); // X aCC 392
+    assert ( ellCount (pList) == 0 );
 
-    ellInit ( &tmpList );             // X aCC 392
+    ellInit ( &tmpList );
 
     /*
      * Check to see if the user has disabled
@@ -217,12 +217,12 @@ extern "C" void epicsShareAPI configureChannelAccessAddressList
     if (yes) {
 		ELLLIST bcastList;
         osiSockAddr addr;
-		ellInit ( &bcastList ); // X aCC 392
+		ellInit ( &bcastList );
         addr.ia.sin_family = AF_UNSPEC;
         osiSockDiscoverBroadcastAddresses ( &bcastList, sock, &addr );
         forcePort ( &bcastList, port );
 		removeDuplicateAddresses ( &tmpList, &bcastList, 1 );
-        if ( ellCount ( &tmpList ) == 0 ) { // X aCC 392
+        if ( ellCount ( &tmpList ) == 0 ) {
             osiSockAddrNode *pNewNode;
             pNewNode = (osiSockAddrNode *) calloc ( 1, sizeof (*pNewNode) );
             if ( pNewNode ) {
@@ -254,11 +254,11 @@ extern "C" void epicsShareAPI printChannelAccessAddressList ( const ELLLIST *pLi
     osiSockAddrNode *pNode;
 
     ::printf ( "Channel Access Address List\n" );
-    pNode = (osiSockAddrNode *) ellFirst ( pList );           // X aCC 749
+    pNode = (osiSockAddrNode *) ellFirst ( pList );
     while (pNode) {
         char buf[64];
         ipAddrToA ( &pNode->addr.ia, buf, sizeof ( buf ) );
         ::printf ( "%s\n", buf );
-        pNode = (osiSockAddrNode *) ellNext ( &pNode->node ); // X aCC 749
+        pNode = (osiSockAddrNode *) ellNext ( &pNode->node );
     }
 }
diff --git a/src/ca/msgForMultiplyDefinedPV.cpp b/src/ca/msgForMultiplyDefinedPV.cpp
index 516bb63bb..2f1a45cde 100644
--- a/src/ca/msgForMultiplyDefinedPV.cpp
+++ b/src/ca/msgForMultiplyDefinedPV.cpp
@@ -73,13 +73,6 @@ void msgForMultiplyDefinedPV::operator delete ( void *pCadaver,
 }
 #endif
 
-void * msgForMultiplyDefinedPV::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void msgForMultiplyDefinedPV::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/msgForMultiplyDefinedPV.h b/src/ca/msgForMultiplyDefinedPV.h
index 545adc815..45d3453ac 100644
--- a/src/ca/msgForMultiplyDefinedPV.h
+++ b/src/ca/msgForMultiplyDefinedPV.h
@@ -39,7 +39,7 @@
 #   define epicsExportSharedSymbols
 #endif
 
-class callbackForMultiplyDefinedPV { // X aCC 655
+class callbackForMultiplyDefinedPV {
 public:
     virtual ~callbackForMultiplyDefinedPV () = 0;
     virtual void pvMultiplyDefinedNotify ( 
@@ -64,7 +64,6 @@ private:
     void transactionComplete ( const char * pHostName );
 	msgForMultiplyDefinedPV ( const msgForMultiplyDefinedPV & );
 	msgForMultiplyDefinedPV & operator = ( const msgForMultiplyDefinedPV & );
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
diff --git a/src/ca/nciu.cpp b/src/ca/nciu.cpp
index c5ae941b2..66bbf02a0 100644
--- a/src/ca/nciu.cpp
+++ b/src/ca/nciu.cpp
@@ -76,29 +76,24 @@ nciu::~nciu ()
 // channels are created by the user, and only destroyed by the user
 // using this routine
 void nciu::destroy (
-    epicsGuard < epicsMutex > & guard )
+    CallbackGuard & callbackGuard,
+    epicsGuard < epicsMutex > & mutualExcusionGuard )
 {    
     while ( baseNMIU * pNetIO = this->eventq.first () ) {
-        bool success = this->cacCtx.destroyIO ( guard, pNetIO->getId (), *this );
+        bool success = this->cacCtx.destroyIO ( callbackGuard, mutualExcusionGuard,
+                                                    pNetIO->getId (), *this );
         assert ( success );
     }
     
     // if the claim reply has not returned yet then we will issue
     // the clear channel request to the server when the claim reply
     // arrives and there is no matching nciu in the client
-    if ( this->channelNode::isInstalledInServer ( guard ) ) {
-        this->getPIIU(guard)->clearChannelRequest ( 
-            guard, this->sid, this->id );
+    if ( this->channelNode::isInstalledInServer ( mutualExcusionGuard ) ) {
+        this->getPIIU(mutualExcusionGuard)->clearChannelRequest (
+                        mutualExcusionGuard, this->sid, this->id );
     }
-    this->piiu->uninstallChan ( guard, *this );
-    this->cacCtx.destroyChannel ( guard, *this );
-}
-
-void * nciu::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
+    this->piiu->uninstallChan ( mutualExcusionGuard, *this );
+    this->cacCtx.destroyChannel ( mutualExcusionGuard, *this );
 }
 
 void nciu::operator delete ( void * )
@@ -387,9 +382,12 @@ void nciu::subscribe (
 }
 
 void nciu::ioCancel ( 
-    epicsGuard < epicsMutex > & guard, const ioid & idIn )
+    CallbackGuard & callbackGuard,
+    epicsGuard < epicsMutex > & mutualExclusionGuard,
+    const ioid & idIn )
 {
-    this->cacCtx.destroyIO ( guard, idIn, *this );
+    this->cacCtx.destroyIO ( callbackGuard,
+          mutualExclusionGuard, idIn, *this );
 }
 
 void nciu::ioShow ( 
diff --git a/src/ca/nciu.h b/src/ca/nciu.h
index de070dcea..417e7fd5c 100644
--- a/src/ca/nciu.h
+++ b/src/ca/nciu.h
@@ -121,7 +121,7 @@ private:
     friend class disconnectGovernorTimer;
 };
 
-class privateInterfaceForIO { // X aCC 655
+class privateInterfaceForIO {
 public:
     virtual void ioCompletionNotify ( 
         epicsGuard < epicsMutex > &, class baseNMIU & ) = 0;
@@ -220,6 +220,7 @@ private:
     ca_uint16_t typeCode;
     ca_uint8_t priority; 
     virtual void destroy (
+        CallbackGuard & callbackGuard,
         epicsGuard < epicsMutex > & mutualExclusionGuard );
     void initiateConnect (
         epicsGuard < epicsMutex > & );
@@ -243,7 +244,15 @@ private:
         epicsGuard < epicsMutex > & guard, 
         unsigned type, arrayElementCount nElem, 
         unsigned mask, cacStateNotify &notify, ioid * );
+    // The primary mutex must be released when calling the user's
+    // callback, and therefore a finite interval exists when we are
+    // moving forward with the intent to call the users callback
+    // but the users IO could be deleted during this interval.
+    // To prevent the user's callback from being called after
+    // destroying his IO we must past a guard for the callback
+    // mutex here.
     virtual void ioCancel ( 
+        CallbackGuard & callbackGuard,
         epicsGuard < epicsMutex > & mutualExclusionGuard,
         const ioid & );
     void ioShow ( 
@@ -270,7 +279,6 @@ private:
         epicsGuard < epicsMutex > & guard ) const throw ();
 	nciu ( const nciu & );
 	nciu & operator = ( const nciu & );
-    void * operator new ( size_t );
     void operator delete ( void * );
 };
 
diff --git a/src/ca/netIO.h b/src/ca/netIO.h
index 57273427a..e728d2a1a 100644
--- a/src/ca/netIO.h
+++ b/src/ca/netIO.h
@@ -42,7 +42,7 @@
 
 class privateInterfaceForIO;
 
-class baseNMIU : public tsDLNode < baseNMIU >, // X aCC 655
+class baseNMIU : public tsDLNode < baseNMIU >,
         public chronIntIdRes < baseNMIU > {
 public:
     virtual void destroy ( 
@@ -106,7 +106,6 @@ private:
     const unsigned mask;
     bool subscribed;
     class netSubscription * isSubscription ();
-    void * operator new ( size_t );
     void operator delete ( void * );
     void * operator new ( size_t, 
         tsFreeList < class netSubscription, 1024, epicsMutexNOOP > & );
@@ -147,7 +146,6 @@ protected:
 private:
     cacReadNotify & notify;
     class privateInterfaceForIO & privateChanForIO;
-    void * operator new ( size_t );
     void operator delete ( void * );
     void * operator new ( size_t, 
         tsFreeList < class netReadNotifyIO, 1024, epicsMutexNOOP > & );
@@ -190,7 +188,6 @@ protected:
 private:
     cacWriteNotify & notify;
     privateInterfaceForIO & privateChanForIO;
-    void * operator new ( size_t );
     void operator delete ( void * );
     void * operator new ( size_t, 
         tsFreeList < class netWriteNotifyIO, 1024, epicsMutexNOOP > & );
@@ -237,12 +234,12 @@ inline netSubscription * netSubscription::factory (
     class privateInterfaceForIO & chan, unsigned type, arrayElementCount count, 
     unsigned mask, cacStateNotify &notify )
 {
-    return new ( freeList ) netSubscription ( chan, type, // X aCC 930
+    return new ( freeList ) netSubscription ( chan, type,
                                 count, mask, notify );
 }
 
 inline arrayElementCount netSubscription::getCount (
-    epicsGuard < epicsMutex > & guard, bool allow_zero ) const // X aCC 361
+    epicsGuard < epicsMutex > & guard, bool allow_zero ) const
 {
     //guard.assertIdenticalMutex ( this->mutex );
     arrayElementCount nativeCount = this->privateChanForIO.nativeElementCount ( guard );
@@ -268,7 +265,7 @@ inline netReadNotifyIO * netReadNotifyIO::factory (
     tsFreeList < class netReadNotifyIO, 1024, epicsMutexNOOP > & freeList, 
     privateInterfaceForIO & ioComplNotifIntf, cacReadNotify & notify )
 {
-    return new ( freeList ) netReadNotifyIO ( ioComplNotifIntf, notify ); // X aCC 930
+    return new ( freeList ) netReadNotifyIO ( ioComplNotifIntf, notify );
 }
 
 inline void * netReadNotifyIO::operator new ( size_t size, 
@@ -289,7 +286,7 @@ inline netWriteNotifyIO * netWriteNotifyIO::factory (
     tsFreeList < class netWriteNotifyIO, 1024, epicsMutexNOOP > & freeList, 
     privateInterfaceForIO & ioComplNotifyIntf, cacWriteNotify & notify )
 {
-    return new ( freeList ) netWriteNotifyIO ( ioComplNotifyIntf, notify ); // X aCC 930
+    return new ( freeList ) netWriteNotifyIO ( ioComplNotifyIntf, notify );
 }
 
 inline void * netWriteNotifyIO::operator new ( size_t size, 
diff --git a/src/ca/netReadNotifyIO.cpp b/src/ca/netReadNotifyIO.cpp
index 446b7175d..2e4b8ead6 100644
--- a/src/ca/netReadNotifyIO.cpp
+++ b/src/ca/netReadNotifyIO.cpp
@@ -119,13 +119,6 @@ void netReadNotifyIO::forceSubscriptionUpdate (
 {
 }
 
-void * netReadNotifyIO::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void netReadNotifyIO::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/netSubscription.cpp b/src/ca/netSubscription.cpp
index 9a29ac2b6..fe2426a89 100644
--- a/src/ca/netSubscription.cpp
+++ b/src/ca/netSubscription.cpp
@@ -170,13 +170,6 @@ void netSubscription::forceSubscriptionUpdate (
         guard, chan, *this );
 }
 
-void * netSubscription::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void netSubscription::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/netWriteNotifyIO.cpp b/src/ca/netWriteNotifyIO.cpp
index 68d4992e7..afa9996d5 100644
--- a/src/ca/netWriteNotifyIO.cpp
+++ b/src/ca/netWriteNotifyIO.cpp
@@ -117,14 +117,6 @@ void netWriteNotifyIO::forceSubscriptionUpdate (
 {
 }
 
-void * netWriteNotifyIO::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( 
-        "why is the compiler calling private operator new" );
-}
-
 void netWriteNotifyIO::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/netiiu.h b/src/ca/netiiu.h
index 99ea128f1..2caa3d0fa 100644
--- a/src/ca/netiiu.h
+++ b/src/ca/netiiu.h
@@ -35,7 +35,7 @@ union osiSockAddr;
 class cac;
 class nciu;
 
-class netiiu { // X aCC 655
+class netiiu {
 public:
     virtual ~netiiu () = 0;
     virtual unsigned getHostName ( 
diff --git a/src/ca/oldAccess.h b/src/ca/oldAccess.h
index d18a4fe1b..5684b83c3 100644
--- a/src/ca/oldAccess.h
+++ b/src/ca/oldAccess.h
@@ -53,7 +53,8 @@ public:
         const char * pName, caCh * pConnCallBackIn, 
         void * pPrivateIn, capri priority );
     void destructor ( 
-        epicsGuard < epicsMutex > & guard );
+        CallbackGuard & cbGuard,
+        epicsGuard < epicsMutex > & mutexGuard );
 
     // legacy C API
     friend unsigned epicsShareAPI ca_get_host_name ( 
@@ -122,6 +123,7 @@ public:
         unsigned type, arrayElementCount count, const void *pValue, 
         cacWriteNotify &, cacChannel::ioid *pId = 0 );
     void ioCancel ( 
+        CallbackGuard & callbackGuard,
         epicsGuard < epicsMutex > & mutualExclusionGuard, 
         const cacChannel::ioid & );
     void ioShow ( 
@@ -162,7 +164,6 @@ private:
         unsigned type, arrayElementCount count );
 	oldChannelNotify ( const oldChannelNotify & );
 	oldChannelNotify & operator = ( const oldChannelNotify & );
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
@@ -195,7 +196,6 @@ private:
         const char *pContext, unsigned type, arrayElementCount count );
 	getCopy ( const getCopy & );
 	getCopy & operator = ( const getCopy & );
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
@@ -221,7 +221,6 @@ private:
         const char * pContext, unsigned type, arrayElementCount count );
 	getCallback ( const getCallback & );
 	getCallback & operator = ( const getCallback & );
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
@@ -245,7 +244,6 @@ private:
         unsigned type, arrayElementCount count );
 	putCallback ( const putCallback & );
 	putCallback & operator = ( const putCallback & );
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
@@ -259,8 +257,16 @@ public:
         evid * );
     ~oldSubscription ();
     oldChannelNotify & channel () const;
+    // The primary mutex must be released when calling the user's
+    // callback, and therefore a finite interval exists when we are
+    // moving forward with the intent to call the users callback
+    // but the users IO could be deleted during this interval.
+    // To prevent the user's callback from being called after
+    // destroying his IO we must past a guard for the callback
+    // mutex here.
     void cancel ( 
-        epicsGuard < epicsMutex > & guard );
+        CallbackGuard & callbackGuard,
+        epicsGuard < epicsMutex > & mutualExclusionGuard );
     void * operator new ( size_t size, 
         tsFreeList < struct oldSubscription, 1024, epicsMutexNOOP > & );
     epicsPlacementDeleteOperator (( void *, 
@@ -278,7 +284,6 @@ private:
         const char *pContext, unsigned type, arrayElementCount count );
 	oldSubscription ( const oldSubscription & );
 	oldSubscription & operator = ( const oldSubscription & );
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
@@ -341,6 +346,8 @@ public:
     void destroySubscription ( epicsGuard < epicsMutex > &, oldSubscription & );
     epicsMutex & mutexRef () const;
 
+    template < class T >
+    void whenThereIsAnExceptionDestroySyncGroupIO ( epicsGuard < epicsMutex > &, T & );
 
     // legacy C API    
     friend int epicsShareAPI ca_create_channel (
@@ -368,6 +375,17 @@ public:
     friend int epicsShareAPI ca_sg_block ( const CA_SYNC_GID gid, ca_real timeout );
     friend int epicsShareAPI ca_sg_reset ( const CA_SYNC_GID gid );
     friend int epicsShareAPI ca_sg_test ( const CA_SYNC_GID gid );
+    friend int epicsShareAPI ca_sg_array_get ( const CA_SYNC_GID gid,
+                              chtype type, arrayElementCount count,
+                              chid pChan, void *pValue );
+    friend int epicsShareAPI ca_sg_array_put ( const CA_SYNC_GID gid,
+                              chtype type, arrayElementCount count,
+                              chid pChan, const void *pValue );
+    friend int ca_sync_group_destroy ( CallbackGuard & cbGuard,
+                                 epicsGuard < epicsMutex > & guard,
+                                ca_client_context & cac, const CA_SYNC_GID gid );
+    friend void sync_group_reset ( ca_client_context & client, 
+                                                  CASG & sg );
 
     // exceptions
     class noSocket {};
@@ -384,7 +402,7 @@ private:
     epicsEvent ioDone;
     epicsEvent callbackThreadActivityComplete;
     epicsThreadId createdByThread;
-    epics_auto_ptr < epicsGuard < epicsMutex > > pCallbackGuard;
+    epics_auto_ptr < CallbackGuard > pCallbackGuard;
     epics_auto_ptr < cacContext > pServiceContext;
     caExceptionHandler * ca_exception_func;
     void * ca_exception_arg;
@@ -444,10 +462,11 @@ inline void oldChannelNotify::initiateConnect (
 }
 
 inline void oldChannelNotify::ioCancel (    
-    epicsGuard < epicsMutex > & guard, 
+    CallbackGuard & callbackGuard,
+    epicsGuard < epicsMutex > & mutualExclusionGuard,
     const cacChannel::ioid & id )
 {
-    this->io.ioCancel ( guard, id );
+    this->io.ioCancel ( callbackGuard, mutualExclusionGuard, id );
 }
 
 inline void oldChannelNotify::ioShow ( 
@@ -492,9 +511,10 @@ inline void oldSubscription::operator delete ( void *pCadaver,
 #endif
 
 inline void oldSubscription::cancel ( 
-    epicsGuard < epicsMutex > & guard ) 
+    CallbackGuard & callbackGuard,
+    epicsGuard < epicsMutex > & mutualExclusionGuard )
 {
-    this->chan.ioCancel ( guard, this->id );
+    this->chan.ioCancel ( callbackGuard, mutualExclusionGuard, this->id );
 }
 
 inline oldChannelNotify & oldSubscription::channel () const
@@ -560,5 +580,32 @@ inline unsigned ca_client_context::sequenceNumberOfOutstandingIO (
     // perhaps on SMP systems THERE should be lock/unlock around this
     return this->ioSeqNo;
 }
+
+template < class T >
+void ca_client_context :: whenThereIsAnExceptionDestroySyncGroupIO ( 
+                            epicsGuard < epicsMutex > & guard, T & io )
+{
+    if ( this->pCallbackGuard.get() &&
+        this->createdByThread == epicsThreadGetIdSelf () ) {
+        io.destroy ( *this->pCallbackGuard.get(), guard );
+    }
+    else {
+        // dont reverse the lock hierarchy
+        epicsGuardRelease < epicsMutex > guardRelease ();
+        {
+            //
+            // we will definately stall out here if all of the
+            // following are true
+            //
+            // o user creates non-preemtive mode client library context
+            // o user doesnt periodically call a ca function
+            // o user calls this function from an auxiillary thread
+            //
+            CallbackGuard cbGuard ( this->cbMutex );
+            epicsGuard < epicsMutex > guard ( this->mutex );
+            io.destroy ( cbGuard, guard );
+        }
+    }
+}
         
 #endif // ifndef oldAccessh
diff --git a/src/ca/oldChannelNotify.cpp b/src/ca/oldChannelNotify.cpp
index 8865f8d63..289c4e8b4 100644
--- a/src/ca/oldChannelNotify.cpp
+++ b/src/ca/oldChannelNotify.cpp
@@ -65,14 +65,15 @@ oldChannelNotify::~oldChannelNotify ()
 }
 
 void  oldChannelNotify::destructor (
-    epicsGuard < epicsMutex > & guard )
+    CallbackGuard & cbGuard,
+    epicsGuard < epicsMutex > & mutexGuard )
 {
-    guard.assertIdenticalMutex ( this->cacCtx.mutexRef () );
-    this->io.destroy ( guard );
+    mutexGuard.assertIdenticalMutex ( this->cacCtx.mutexRef () );
+    this->io.destroy ( cbGuard, mutexGuard );
     // no need to worry about a connect preempting here because
     // the io (the nciu) has been destroyed above
     if ( this->pConnCallBack == 0 && ! this->currentlyConnected ) {
-        this->cacCtx.decrementOutstandingIO ( guard, this->ioSeqNo );
+        this->cacCtx.decrementOutstandingIO ( mutexGuard, this->ioSeqNo );
     }
     this->~oldChannelNotify ();
 }
@@ -159,13 +160,6 @@ void oldChannelNotify::writeException (
         __FILE__, __LINE__, *this, type, count, CA_OP_PUT );
 }
 
-void * oldChannelNotify::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void oldChannelNotify::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
@@ -638,7 +632,7 @@ arrayElementCount epicsShareAPI ca_element_count ( chid pChan )
 /*
  * ca_state ()
  */
-enum channel_state epicsShareAPI ca_state ( chid pChan ) // X aCC 361
+enum channel_state epicsShareAPI ca_state ( chid pChan )
 {
     epicsGuard < epicsMutex > guard ( pChan->cacCtx.mutexRef () );
     if ( pChan->io.connected ( guard ) ) {
diff --git a/src/ca/putCallback.cpp b/src/ca/putCallback.cpp
index bff1dd8a4..ba17a654c 100644
--- a/src/ca/putCallback.cpp
+++ b/src/ca/putCallback.cpp
@@ -90,13 +90,6 @@ void putCallback::exception (
     }
 }
 
-void * putCallback::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void putCallback::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/repeater.cpp b/src/ca/repeater.cpp
index 64016aed6..ef271e461 100644
--- a/src/ca/repeater.cpp
+++ b/src/ca/repeater.cpp
@@ -178,7 +178,7 @@ bool repeaterClient::connect ()
     return true;
 }
 
-bool repeaterClient::sendConfirm () // X aCC 361
+bool repeaterClient::sendConfirm ()
 {
     int status;
 
@@ -204,7 +204,7 @@ bool repeaterClient::sendConfirm () // X aCC 361
     }
 }
 
-bool repeaterClient::sendMessage ( const void *pBuf, unsigned bufSize ) // X aCC 361
+bool repeaterClient::sendMessage ( const void *pBuf, unsigned bufSize )
 {
     int status;
 
@@ -245,13 +245,6 @@ repeaterClient::~repeaterClient ()
 #endif
 }
 
-void * repeaterClient::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void repeaterClient::operator delete ( void * )
 { 
     // Visual C++ .net appears to require operator delete if
@@ -304,7 +297,7 @@ inline bool repeaterClient::identicalPort ( const osiSockAddr &fromIn )
     return false;
 }
 
-bool repeaterClient::verify ()  // X aCC 361
+bool repeaterClient::verify ()
 {
     SOCKET tmpSock;
     bool success = makeSocket ( this->port (), false, & tmpSock );
diff --git a/src/ca/repeaterClient.h b/src/ca/repeaterClient.h
index c57aeaefe..faaf0809f 100644
--- a/src/ca/repeaterClient.h
+++ b/src/ca/repeaterClient.h
@@ -64,7 +64,6 @@ private:
     osiSockAddr from;
     SOCKET sock;
     unsigned short port () const;
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
diff --git a/src/ca/repeaterSubscribeTimer.cpp b/src/ca/repeaterSubscribeTimer.cpp
index 337ff00ba..69362da5f 100644
--- a/src/ca/repeaterSubscribeTimer.cpp
+++ b/src/ca/repeaterSubscribeTimer.cpp
@@ -64,7 +64,7 @@ void repeaterSubscribeTimer::shutdown (
 }
 
 epicsTimerNotify::expireStatus repeaterSubscribeTimer::
-    expire ( const epicsTime & /* currentTime */ )  // X aCC 361
+    expire ( const epicsTime & /* currentTime */ )
 {
     static const unsigned nTriesToMsg = 50;
     if ( this->attempts > nTriesToMsg && ! this->once ) {
diff --git a/src/ca/repeaterSubscribeTimer.h b/src/ca/repeaterSubscribeTimer.h
index 0a23d16d3..52f146d6e 100644
--- a/src/ca/repeaterSubscribeTimer.h
+++ b/src/ca/repeaterSubscribeTimer.h
@@ -43,7 +43,7 @@
 class epicsMutex;
 class cacContextNotify;
 
-class repeaterTimerNotify { // X aCC 655
+class repeaterTimerNotify {
 public:
     virtual ~repeaterTimerNotify () = 0;
     virtual void repeaterRegistrationMessage ( 
diff --git a/src/ca/searchTimer.cpp b/src/ca/searchTimer.cpp
index c7aa980ae..e5a8d1c54 100644
--- a/src/ca/searchTimer.cpp
+++ b/src/ca/searchTimer.cpp
@@ -124,7 +124,7 @@ void searchTimer::moveChannels (
 // searchTimer::expire ()
 //
 epicsTimerNotify::expireStatus searchTimer::expire ( 
-    const epicsTime & currentTime ) // X aCC 361
+    const epicsTime & currentTime )
 {
     epicsGuard < epicsMutex > guard ( this->mutex );
 
diff --git a/src/ca/searchTimer.h b/src/ca/searchTimer.h
index 2df980ded..7b9fe1717 100644
--- a/src/ca/searchTimer.h
+++ b/src/ca/searchTimer.h
@@ -43,7 +43,7 @@
 #include "caProto.h"
 #include "netiiu.h"
 
-class searchTimerNotify { // X aCC 655
+class searchTimerNotify {
 public:
     virtual ~searchTimerNotify () = 0;
     virtual void boostChannel ( 
diff --git a/src/ca/sgAutoPtr.h b/src/ca/sgAutoPtr.h
index b3753bb44..a6383d69b 100644
--- a/src/ca/sgAutoPtr.h
+++ b/src/ca/sgAutoPtr.h
@@ -29,8 +29,7 @@
 template < class T >
 class sgAutoPtr {
 public:
-    sgAutoPtr ( epicsGuard < epicsMutex > &, 
-        struct CASG &, tsDLList < syncGroupNotify > & );
+    sgAutoPtr ( epicsGuard < epicsMutex > &, struct CASG & );
     ~sgAutoPtr ();
     sgAutoPtr < T > & operator = ( T * );
     T * operator -> ();
@@ -38,7 +37,6 @@ public:
     T * get ();
     T * release ();
 private:
-    tsDLList < syncGroupNotify > & list;
     T * pNotify;
     struct CASG & sg;
     epicsGuard < epicsMutex > & guard;
@@ -47,9 +45,8 @@ private:
 
 template < class T >
 inline sgAutoPtr < T > :: sgAutoPtr ( 
-    epicsGuard < epicsMutex > & guardIn, 
-    struct CASG & sgIn, tsDLList < syncGroupNotify > & listIn  ) : 
-    list ( listIn ), pNotify ( 0 ), sg ( sgIn ), guard ( guardIn )
+    epicsGuard < epicsMutex > & guardIn, struct CASG & sgIn ) : 
+    pNotify ( 0 ), sg ( sgIn ), guard ( guardIn )
 {
 }
 
@@ -57,8 +54,9 @@ template < class T >
 inline sgAutoPtr < T > :: ~sgAutoPtr () 
 {
     if ( this->pNotify ) {
-        list.remove ( *this->pNotify );
-        pNotify->destroy ( this->guard, this->sg );
+        this->sg.ioPendingList.remove ( *this->pNotify );
+        this->sg.client.
+            whenThereIsAnExceptionDestroySyncGroupIO ( this->guard, *this->pNotify );
     }
 }
 
@@ -66,11 +64,12 @@ template < class T >
 inline sgAutoPtr < T > & sgAutoPtr < T > :: operator = ( T * pNotifyIn )
 {
     if ( this->pNotify ) {
-        list.remove ( *this->pNotify );
-        pNotify->destroy ( this->guard, this->sg );
+        this->sg.ioPendingList.remove ( *this->pNotify );
+        this->sg.client.
+            whenThereIsAnExceptionDestroySyncGroupIO ( this->guard, *this->pNotify );
     }
     this->pNotify = pNotifyIn;
-    list.add ( *this->pNotify );
+    this->sg.ioPendingList.add ( *this->pNotify );
     return *this;
 }
 
diff --git a/src/ca/syncGroup.h b/src/ca/syncGroup.h
index c41c9b5b8..f805b6bbd 100644
--- a/src/ca/syncGroup.h
+++ b/src/ca/syncGroup.h
@@ -46,29 +46,17 @@
 
 static const unsigned CASG_MAGIC = 0xFAB4CAFE;
 
-// used to control access to CASG's recycle routines which
-// should only be indirectly invoked by CASG when its lock
-// is applied
-class casgRecycle {             // X aCC 655
-public:
-    virtual void recycleSyncGroupWriteNotify ( 
-        epicsGuard < epicsMutex > &, class syncGroupWriteNotify & io ) = 0;
-    virtual void recycleSyncGroupReadNotify ( 
-        epicsGuard < epicsMutex > &, class syncGroupReadNotify & io ) = 0;
-protected:
-    virtual ~casgRecycle ();
-};
-
 class syncGroupNotify : public tsDLNode < syncGroupNotify > {
 public:
     syncGroupNotify ();
     virtual void destroy (  
-        epicsGuard < epicsMutex > & guard, 
-        casgRecycle & ) = 0;
+        CallbackGuard & cbGuard,
+        epicsGuard < epicsMutex > & guard ) = 0;
     virtual bool ioPending (  
         epicsGuard < epicsMutex > & guard ) = 0;
     virtual void cancel (
-        epicsGuard < epicsMutex > & guard ) = 0;
+        CallbackGuard & cbGuard,
+        epicsGuard < epicsMutex > & mutualExclusionGuard ) = 0;
     virtual void show ( 
         epicsGuard < epicsMutex > &, 
         unsigned level ) const = 0;
@@ -78,33 +66,38 @@ protected:
 	syncGroupNotify & operator = ( const syncGroupNotify & );
 };
 
+struct CASG;
+
 class syncGroupReadNotify : public syncGroupNotify, public cacReadNotify {
 public:
+    typedef void ( CASG :: * PRecycleFunc ) 
+        ( epicsGuard < epicsMutex > &, syncGroupReadNotify & );
     static syncGroupReadNotify * factory ( 
         tsFreeList < class syncGroupReadNotify, 128, epicsMutexNOOP > &, 
-        struct CASG &, chid, void *pValueIn );
+        CASG &, PRecycleFunc, chid, void *pValueIn );
     void destroy (  
-        epicsGuard < epicsMutex > & guard, 
-        casgRecycle & );
+        CallbackGuard & cbGuard,
+        epicsGuard < epicsMutex > & guard );
     bool ioPending (  
         epicsGuard < epicsMutex > & guard );
     void begin (  epicsGuard < epicsMutex > &, 
         unsigned type, arrayElementCount count );
     void cancel (
+        CallbackGuard & cbGuard,
         epicsGuard < epicsMutex > & guard );
     void show (  epicsGuard < epicsMutex > &, unsigned level ) const;
 protected:
-    syncGroupReadNotify ( struct CASG & sgIn, chid, void * pValueIn );
+    syncGroupReadNotify ( CASG & sgIn, PRecycleFunc, chid, void * pValueIn );
     virtual ~syncGroupReadNotify ();
 private:
     chid chan;
-    struct CASG & sg;
+    PRecycleFunc pRecycleFunc;
+    CASG & sg;
     void * pValue;
     const unsigned magic;
     cacChannel::ioid id;
     bool idIsValid;
     bool ioComplete;
-    void * operator new ( size_t );
     void operator delete ( void * );
     void * operator new ( size_t, 
         tsFreeList < class syncGroupReadNotify, 128, epicsMutexNOOP > & );
@@ -122,30 +115,33 @@ private:
 
 class syncGroupWriteNotify : public syncGroupNotify, public cacWriteNotify {
 public:
+    typedef void ( CASG :: * PRecycleFunc ) 
+        ( epicsGuard < epicsMutex > &, syncGroupWriteNotify & );
     static syncGroupWriteNotify * factory ( 
         tsFreeList < class syncGroupWriteNotify, 128, epicsMutexNOOP > &, 
-        struct CASG &, chid );
+        CASG &, PRecycleFunc, chid );
     void destroy (  
-        epicsGuard < epicsMutex > & guard, 
-        casgRecycle & );
+        CallbackGuard & cbGuard,
+        epicsGuard < epicsMutex > & guard );
     bool ioPending (  
         epicsGuard < epicsMutex > & guard );
     void begin (  epicsGuard < epicsMutex > &, unsigned type, 
         arrayElementCount count, const void * pValueIn );
     void cancel (
+        CallbackGuard & cbGuard,
         epicsGuard < epicsMutex > & guard );
     void show (  epicsGuard < epicsMutex > &, unsigned level ) const;
 protected:
-    syncGroupWriteNotify  ( struct CASG &, chid );
+    syncGroupWriteNotify  ( struct CASG &, PRecycleFunc, chid );
     virtual ~syncGroupWriteNotify (); // allocate only from pool
 private:
     chid chan;
-    struct CASG & sg;
+    PRecycleFunc pRecycleFunc;
+    CASG & sg;
     const unsigned magic;
     cacChannel::ioid id;
     bool idIsValid;
     bool ioComplete;
-    void * operator new ( size_t );
     void operator delete ( void * );
     void * operator new ( size_t, 
         tsFreeList < class syncGroupWriteNotify, 128, epicsMutexNOOP > & );
@@ -163,17 +159,19 @@ struct ca_client_context;
 
 template < class T > class sgAutoPtr;
 
-struct CASG : public chronIntIdRes < CASG >, private casgRecycle {
+struct CASG : public chronIntIdRes < CASG > {
 public:
     CASG ( epicsGuard < epicsMutex > &, ca_client_context & cacIn );
     void destructor ( 
+        CallbackGuard &,
         epicsGuard < epicsMutex > & guard );
     bool ioComplete ( 
+        CallbackGuard &,
         epicsGuard < epicsMutex > & guard );
     bool verify ( epicsGuard < epicsMutex > & ) const;
     int block ( epicsGuard < epicsMutex > * pcbGuard, 
         epicsGuard < epicsMutex > & guard, double timeout );
-    void reset ( epicsGuard < epicsMutex > & guard );
+    void reset ( CallbackGuard &, epicsGuard < epicsMutex > & );
     void show ( epicsGuard < epicsMutex > &, unsigned level ) const;
     void show ( unsigned level ) const;
     void get ( epicsGuard < epicsMutex > &, chid pChan, 
@@ -194,6 +192,7 @@ public:
         tsFreeList < struct CASG, 128, epicsMutexNOOP  > & );
     epicsPlacementDeleteOperator (( void *, 
         tsFreeList < struct CASG, 128, epicsMutexNOOP > & ))
+
 private:
     tsDLList < syncGroupNotify > ioPendingList;
     tsDLList < syncGroupNotify > ioCompletedList;
@@ -202,20 +201,21 @@ private:
     unsigned magic;
     tsFreeList < class syncGroupReadNotify, 128, epicsMutexNOOP > freeListReadOP;
     tsFreeList < class syncGroupWriteNotify, 128, epicsMutexNOOP > freeListWriteOP;
-    void recycleSyncGroupWriteNotify (  
-        epicsGuard < epicsMutex > &, syncGroupWriteNotify & io );
-    void recycleSyncGroupReadNotify (  
-        epicsGuard < epicsMutex > &, syncGroupReadNotify & io );
 
     void destroyPendingIO ( 
+        CallbackGuard & cbGuard,
         epicsGuard < epicsMutex > & guard );
     void destroyCompletedIO ( 
+        CallbackGuard & cbGuard,
         epicsGuard < epicsMutex > & guard );
+    void recycleReadNotifyIO ( epicsGuard < epicsMutex > &, 
+                                syncGroupReadNotify & );
+    void recycleWriteNotifyIO ( epicsGuard < epicsMutex > &, 
+                                syncGroupWriteNotify & );
 
 	CASG ( const CASG & );
 	CASG & operator = ( const CASG & );
 
-    void * operator new ( size_t size );
     void operator delete ( void * );
 
     ~CASG ();
diff --git a/src/ca/syncGroupReadNotify.cpp b/src/ca/syncGroupReadNotify.cpp
index 11f90fe57..33ba5fb32 100644
--- a/src/ca/syncGroupReadNotify.cpp
+++ b/src/ca/syncGroupReadNotify.cpp
@@ -27,8 +27,10 @@
 #include "oldAccess.h"
 
 syncGroupReadNotify::syncGroupReadNotify ( 
-    CASG & sgIn, chid pChan, void * pValueIn ) :
-    chan ( pChan ), sg ( sgIn ), pValue ( pValueIn ), 
+    CASG & sgIn, PRecycleFunc pRecycleFuncIn,
+    chid pChan, void * pValueIn ) :
+    chan ( pChan ), pRecycleFunc ( pRecycleFuncIn ), 
+    sg ( sgIn ), pValue ( pValueIn ),
     magic ( CASG_MAGIC ), id ( 0u ), 
     idIsValid ( false ), ioComplete ( false )
 {
@@ -46,27 +48,30 @@ void syncGroupReadNotify::begin (
 }
 
 void syncGroupReadNotify::cancel ( 
-    epicsGuard < epicsMutex > & guard )
+    CallbackGuard & callbackGuard,
+    epicsGuard < epicsMutex > & mutualExcusionGuard )
 {
     if ( this->idIsValid ) {
-        this->chan->ioCancel ( guard, this->id );
+        this->chan->ioCancel ( callbackGuard, mutualExcusionGuard, this->id );
         this->idIsValid = false;
     }
 }
 
 syncGroupReadNotify * syncGroupReadNotify::factory ( 
     tsFreeList < class syncGroupReadNotify, 128, epicsMutexNOOP > & freeList, 
-    struct CASG & sg, chid chan, void * pValueIn )
+    struct CASG & sg, PRecycleFunc pRecycleFunc, chid chan, void * pValueIn )
 {
-    return new ( freeList ) // X aCC 930
-        syncGroupReadNotify ( sg, chan, pValueIn );
+    return new ( freeList )
+        syncGroupReadNotify ( sg, pRecycleFunc, chan, pValueIn );
 }
 
 void syncGroupReadNotify::destroy ( 
-    epicsGuard < epicsMutex > & guard, casgRecycle & recycle )
+    CallbackGuard &,
+    epicsGuard < epicsMutex > & guard )
 {
+    CASG & sgRef ( this->sg );
     this->~syncGroupReadNotify ();
-    recycle.recycleSyncGroupReadNotify ( guard, *this );
+    ( sgRef.*pRecycleFunc ) ( guard, *this );
 }
 
 syncGroupReadNotify::~syncGroupReadNotify ()
@@ -122,13 +127,6 @@ void syncGroupReadNotify::show (
     }
 }
 
-void * syncGroupReadNotify::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void syncGroupReadNotify::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/syncGroupWriteNotify.cpp b/src/ca/syncGroupWriteNotify.cpp
index 244d9d3bd..fed76ed81 100644
--- a/src/ca/syncGroupWriteNotify.cpp
+++ b/src/ca/syncGroupWriteNotify.cpp
@@ -26,8 +26,10 @@
 #include "syncGroup.h"
 #include "oldAccess.h"
 
-syncGroupWriteNotify::syncGroupWriteNotify ( CASG & sgIn, chid pChan ) :
-    chan ( pChan ), sg ( sgIn ), magic ( CASG_MAGIC ), 
+syncGroupWriteNotify::syncGroupWriteNotify ( CASG & sgIn, 
+                      PRecycleFunc pRecycleFuncIn, chid pChan ) :
+    chan ( pChan ), pRecycleFunc ( pRecycleFuncIn ),
+    sg ( sgIn ), magic ( CASG_MAGIC ),
         id ( 0u ), idIsValid ( false ), ioComplete ( false )
 {
 }
@@ -45,26 +47,29 @@ void syncGroupWriteNotify::begin (
 }
 
 void syncGroupWriteNotify::cancel ( 
-    epicsGuard < epicsMutex > & guard )
+    CallbackGuard & callbackGuard,
+    epicsGuard < epicsMutex > & mutualExcusionGuard )
 {
     if ( this->idIsValid ) {
-        this->chan->ioCancel ( guard, this->id );
+        this->chan->ioCancel ( callbackGuard, mutualExcusionGuard, this->id );
         this->idIsValid = false;
     }
 }
 
 syncGroupWriteNotify * syncGroupWriteNotify::factory ( 
     tsFreeList < class syncGroupWriteNotify, 128, epicsMutexNOOP > &freeList, 
-    struct CASG & sg, chid chan )
+    struct CASG & sg, PRecycleFunc pRecycleFunc, chid chan )
 {
-    return new ( freeList ) syncGroupWriteNotify ( sg, chan );
+    return new ( freeList ) syncGroupWriteNotify ( sg, pRecycleFunc, chan );
 }
 
 void syncGroupWriteNotify::destroy ( 
-    epicsGuard < epicsMutex > & guard, casgRecycle & recycle )
+    CallbackGuard &,
+    epicsGuard < epicsMutex > & guard )
 {
+    CASG & sgRef ( this->sg );
     this->~syncGroupWriteNotify ();
-    recycle.recycleSyncGroupWriteNotify ( guard, *this );
+    ( sgRef.*pRecycleFunc ) ( guard, *this );
 }
 
 syncGroupWriteNotify::~syncGroupWriteNotify ()
@@ -112,13 +117,6 @@ void syncGroupWriteNotify::show (
     }
 }
 
-void * syncGroupWriteNotify::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void syncGroupWriteNotify::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if
diff --git a/src/ca/syncgrp.cpp b/src/ca/syncgrp.cpp
index c76f6a194..cb7a7cffa 100644
--- a/src/ca/syncgrp.cpp
+++ b/src/ca/syncgrp.cpp
@@ -23,7 +23,7 @@
 /*
  * ca_sg_create()
  */
-extern "C" int epicsShareAPI ca_sg_create ( CA_SYNC_GID * pgid ) // X aCC 361
+extern "C" int epicsShareAPI ca_sg_create ( CA_SYNC_GID * pgid )
 {
     ca_client_context * pcac;
     int caStatus;
@@ -48,6 +48,22 @@ extern "C" int epicsShareAPI ca_sg_create ( CA_SYNC_GID * pgid ) // X aCC 361
     }
 }
 
+int ca_sync_group_destroy ( CallbackGuard & cbGuard, epicsGuard < epicsMutex > & guard,
+                                ca_client_context & cac, const CA_SYNC_GID gid )
+{
+    int caStatus;
+    CASG * pcasg = cac.lookupCASG ( guard, gid );
+    if ( pcasg ) {
+        pcasg->destructor ( cbGuard, guard );
+        cac.casgFreeList.release ( pcasg );
+        caStatus = ECA_NORMAL;
+    }
+    else {
+        caStatus = ECA_BADSYNCGRP;
+    }
+    return caStatus;
+}
+
 /*
  * ca_sg_delete()
  */
@@ -56,19 +72,51 @@ extern "C" int epicsShareAPI ca_sg_delete ( const CA_SYNC_GID gid )
     ca_client_context * pcac;
     int caStatus = fetchClientContext ( & pcac );
     if ( caStatus == ECA_NORMAL ) {
-        epicsGuard < epicsMutex > guard ( pcac->mutexRef() );
-        CASG * pcasg = pcac->lookupCASG ( guard, gid );
-        if ( pcasg ) {
-            pcasg->destructor ( guard );
-            pcac->casgFreeList.release ( pcasg );
+        if ( pcac->pCallbackGuard.get() &&
+            pcac->createdByThread == epicsThreadGetIdSelf () ) {
+          epicsGuard < epicsMutex > guard ( pcac->mutex );
+          caStatus = ca_sync_group_destroy ( *pcac->pCallbackGuard.get(),
+                                          guard, *pcac, gid );
         }
         else {
-            caStatus = ECA_BADSYNCGRP;
+          //
+          // we will definately stall out here if all of the
+          // following are true
+          //
+          // o user creates non-preemtive mode client library context
+          // o user doesnt periodically call a ca function
+          // o user calls this function from an auxiillary thread
+          //
+          CallbackGuard cbGuard ( pcac->cbMutex );
+          epicsGuard < epicsMutex > guard ( pcac->mutex );
+          caStatus = ca_sync_group_destroy ( cbGuard, guard, *pcac, gid );
         }
     }
     return caStatus;
 }
 
+void sync_group_reset ( ca_client_context & client, CASG & sg )
+{
+    if ( client.pCallbackGuard.get() &&
+        client.createdByThread == epicsThreadGetIdSelf () ) {
+        epicsGuard < epicsMutex > guard ( client.mutex );
+        sg.reset ( *client.pCallbackGuard.get(), guard );
+    }
+    else {  
+        //
+        // we will definately stall out here if all of the
+        // following are true
+        //
+        // o user creates non-preemtive mode client library context
+        // o user doesnt periodically call a ca function
+        // o user calls this function from an auxiillary thread
+        //
+        CallbackGuard cbGuard ( client.cbMutex );
+        epicsGuard < epicsMutex > guard ( client.mutex );
+        sg.reset ( cbGuard, guard );
+    }
+}
+
 //
 // ca_sg_block ()
 //
@@ -84,14 +132,20 @@ extern "C" int epicsShareAPI ca_sg_block (
     ca_client_context *pcac;
     int status = fetchClientContext ( &pcac );
     if ( status == ECA_NORMAL ) {
+        CASG * pcasg;
+        {
         epicsGuard < epicsMutex > guard ( pcac->mutex );
-        CASG * pcasg = pcac->lookupCASG ( guard, gid );
-        if ( ! pcasg ) {
-            status = ECA_BADSYNCGRP;
-        }
-        else {
+          pcasg = pcac->lookupCASG ( guard, gid );
+          if ( pcasg ) {
             status = pcasg->block ( 
                 pcac->pCallbackGuard.get (), guard, timeout );
+          }
+          else {
+              status = ECA_BADSYNCGRP;
+          }
+        }
+        if ( pcasg ) {
+            sync_group_reset ( *pcac, *pcasg );
         }
     }
     return status;
@@ -105,10 +159,14 @@ extern "C" int epicsShareAPI ca_sg_reset ( const CA_SYNC_GID gid )
     ca_client_context *pcac;
     int caStatus = fetchClientContext (&pcac);
     if ( caStatus == ECA_NORMAL ) {
+        CASG * pcasg;
+        {
         epicsGuard < epicsMutex > guard ( pcac->mutex );
-        CASG * pcasg = pcac->lookupCASG ( guard, gid );
+            pcasg = pcac->lookupCASG ( guard, gid );
+        }
         if ( pcasg ) {
-            pcasg->reset ( guard );
+            sync_group_reset ( *pcac, *pcasg );
+            caStatus = ECA_NORMAL;
         }
         else {
             caStatus = ECA_BADSYNCGRP;
@@ -143,7 +201,7 @@ extern "C" int epicsShareAPI ca_sg_stat ( const CA_SYNC_GID gid )
 /*
  * ca_sg_test
  */
-extern "C" int epicsShareAPI ca_sg_test ( const CA_SYNC_GID gid ) // X aCC 361
+extern "C" int epicsShareAPI ca_sg_test ( const CA_SYNC_GID gid )
 {
     ca_client_context * pcac;
     int caStatus = fetchClientContext ( &pcac );
@@ -151,7 +209,26 @@ extern "C" int epicsShareAPI ca_sg_test ( const CA_SYNC_GID gid ) // X aCC 361
         epicsGuard < epicsMutex > guard ( pcac->mutexRef() );
         CASG * pcasg = pcac->lookupCASG ( guard, gid );
         if ( pcasg ) {
-            if ( pcasg->ioComplete ( guard ) ) {
+            bool isComplete;
+            if ( pcac->pCallbackGuard.get() &&
+                pcac->createdByThread == epicsThreadGetIdSelf () ) {
+              epicsGuard < epicsMutex > guard ( pcac->mutex );
+              isComplete = pcasg->ioComplete ( *pcac->pCallbackGuard.get(), guard );
+            }
+            else {
+              //
+              // we will definately stall out here if all of the
+              // following are true
+              //
+              // o user creates non-preemtive mode client library context
+              // o user doesnt periodically call a ca function
+              // o user calls this function from an auxiillary thread
+              //
+              CallbackGuard cbGuard ( pcac->cbMutex );
+              epicsGuard < epicsMutex > guard ( pcac->mutex );
+              isComplete = pcasg->ioComplete ( cbGuard, guard );
+            }
+            if ( isComplete ) {
                 caStatus = ECA_IODONE;
             }
             else{
@@ -172,17 +249,14 @@ extern "C" int epicsShareAPI ca_sg_array_put ( const CA_SYNC_GID gid, chtype typ
     arrayElementCount count, chid pChan, const void *pValue )
 {
     ca_client_context *pcac;
-    CASG *pcasg;
-    int caStatus;
     
-    caStatus = fetchClientContext ( &pcac );
+    int caStatus = fetchClientContext ( &pcac );
     if ( caStatus != ECA_NORMAL ) {
         return caStatus;
     }
 
     epicsGuard < epicsMutex > guard ( pcac->mutexRef() );
-
-    pcasg = pcac->lookupCASG ( guard, gid );
+    CASG * const pcasg = pcac->lookupCASG ( guard, gid );
     if ( ! pcasg ) {
         return ECA_BADSYNCGRP;
     }
@@ -237,17 +311,14 @@ extern "C" int epicsShareAPI ca_sg_array_get ( const CA_SYNC_GID gid, chtype typ
     arrayElementCount count, chid pChan, void *pValue )
 {
     ca_client_context *pcac;
-    CASG *pcasg;
-    int caStatus;
 
-    caStatus = fetchClientContext ( &pcac );
+    int caStatus = fetchClientContext ( &pcac );
     if ( caStatus != ECA_NORMAL ) {
         return caStatus;
     }
 
     epicsGuard < epicsMutex > guard ( pcac->mutexRef() );
-
-    pcasg = pcac->lookupCASG ( guard, gid );
+    CASG * const pcasg = pcac->lookupCASG ( guard, gid );
     if ( ! pcasg ) {
         return ECA_BADSYNCGRP;
     }
diff --git a/src/ca/tcpRecvWatchdog.cpp b/src/ca/tcpRecvWatchdog.cpp
index 35e509a7c..72c92968b 100644
--- a/src/ca/tcpRecvWatchdog.cpp
+++ b/src/ca/tcpRecvWatchdog.cpp
@@ -45,7 +45,7 @@ tcpRecvWatchdog::~tcpRecvWatchdog ()
 }
 
 epicsTimerNotify::expireStatus
-tcpRecvWatchdog::expire ( const epicsTime & /* currentTime */ ) // X aCC 361
+tcpRecvWatchdog::expire ( const epicsTime & /* currentTime */ )
 {
     epicsGuard < epicsMutex > guard ( this->mutex );
     if ( this->shuttingDown ) {
diff --git a/src/ca/tcpiiu.cpp b/src/ca/tcpiiu.cpp
index 9cf9f6f4d..377e3ac3c 100644
--- a/src/ca/tcpiiu.cpp
+++ b/src/ca/tcpiiu.cpp
@@ -1135,7 +1135,7 @@ void tcpiiu::show ( unsigned level ) const
     }
 }
 
-bool tcpiiu::setEchoRequestPending ( epicsGuard < epicsMutex > & guard ) // X aCC 361
+bool tcpiiu::setEchoRequestPending ( epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
 
@@ -1275,12 +1275,9 @@ bool tcpiiu::processIncoming (
         this->msgHeaderAvailable = false;
         this->curDataBytes = 0u;
     }
-#   if defined ( __HP_aCC ) && _HP_aCC <= 033300
-        return false; // to make hpux compiler happy...
-#   endif
 }
 
-void tcpiiu::hostNameSetRequest ( epicsGuard < epicsMutex > & guard ) // X aCC 431
+void tcpiiu::hostNameSetRequest ( epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
 
@@ -1310,7 +1307,7 @@ void tcpiiu::hostNameSetRequest ( epicsGuard < epicsMutex > & guard ) // X aCC 4
 /*
  * tcpiiu::userNameSetRequest ()
  */
-void tcpiiu::userNameSetRequest ( epicsGuard < epicsMutex > & guard ) // X aCC 431
+void tcpiiu::userNameSetRequest ( epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
 
@@ -1338,7 +1335,7 @@ void tcpiiu::userNameSetRequest ( epicsGuard < epicsMutex > & guard ) // X aCC 4
 }
 
 void tcpiiu::disableFlowControlRequest ( 
-    epicsGuard < epicsMutex > & guard ) // X aCC 431
+    epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
 
@@ -1354,7 +1351,7 @@ void tcpiiu::disableFlowControlRequest (
 }
 
 void tcpiiu::enableFlowControlRequest ( 
-    epicsGuard < epicsMutex > & guard ) // X aCC 431
+    epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
 
@@ -1369,7 +1366,7 @@ void tcpiiu::enableFlowControlRequest (
     minder.commit ();
 }
 
-void tcpiiu::versionMessage ( epicsGuard < epicsMutex > & guard, // X aCC 431
+void tcpiiu::versionMessage ( epicsGuard < epicsMutex > & guard,
                              const cacChannel::priLev & priority )
 {
     guard.assertIdenticalMutex ( this->mutex );
@@ -1389,7 +1386,7 @@ void tcpiiu::versionMessage ( epicsGuard < epicsMutex > & guard, // X aCC 431
     minder.commit ();
 }
 
-void tcpiiu::echoRequest ( epicsGuard < epicsMutex > & guard ) // X aCC 431
+void tcpiiu::echoRequest ( epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
     
@@ -1410,7 +1407,7 @@ void tcpiiu::echoRequest ( epicsGuard < epicsMutex > & guard ) // X aCC 431
     minder.commit ();
 }
 
-void tcpiiu::writeRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
+void tcpiiu::writeRequest ( epicsGuard < epicsMutex > & guard,
     nciu &chan, unsigned type, arrayElementCount nElem, const void *pValue )
 {
     guard.assertIdenticalMutex ( this->mutex );
@@ -1425,7 +1422,7 @@ void tcpiiu::writeRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
 }
 
 
-void tcpiiu::writeNotifyRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
+void tcpiiu::writeNotifyRequest ( epicsGuard < epicsMutex > & guard,
                                  nciu &chan, netWriteNotifyIO &io, unsigned type,  
                                 arrayElementCount nElem, const void *pValue )
 {
@@ -1444,7 +1441,7 @@ void tcpiiu::writeNotifyRequest ( epicsGuard < epicsMutex > & guard, // X aCC 43
     minder.commit ();
 }
 
-void tcpiiu::readNotifyRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
+void tcpiiu::readNotifyRequest ( epicsGuard < epicsMutex > & guard,
                                nciu & chan, netReadNotifyIO & io, 
                                unsigned dataType, arrayElementCount nElem )
 {
@@ -1477,7 +1474,7 @@ void tcpiiu::readNotifyRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
 }
 
 void tcpiiu::createChannelRequest ( 
-    nciu & chan, epicsGuard < epicsMutex > & guard ) // X aCC 431
+    nciu & chan, epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
 
@@ -1525,7 +1522,7 @@ void tcpiiu::createChannelRequest (
     minder.commit ();
 }
 
-void tcpiiu::clearChannelRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
+void tcpiiu::clearChannelRequest ( epicsGuard < epicsMutex > & guard,
                                   ca_uint32_t sid, ca_uint32_t cid )
 {
     guard.assertIdenticalMutex ( this->mutex );
@@ -1547,7 +1544,7 @@ void tcpiiu::clearChannelRequest ( epicsGuard < epicsMutex > & guard, // X aCC 4
 // is to try again the next time that we reconnect
 //
 void tcpiiu::subscriptionRequest ( 
-    epicsGuard < epicsMutex > & guard, // X aCC 431
+    epicsGuard < epicsMutex > & guard,
     nciu & chan, netSubscription & subscr )
 {
     guard.assertIdenticalMutex ( this->mutex );
@@ -1599,7 +1596,7 @@ void tcpiiu::subscriptionRequest (
 // is to try again the next time that we reconnect
 //
 void tcpiiu::subscriptionUpdateRequest ( 
-    epicsGuard < epicsMutex > & guard, // X aCC 431
+    epicsGuard < epicsMutex > & guard,
     nciu & chan, netSubscription & subscr )
 {
     guard.assertIdenticalMutex ( this->mutex );
@@ -1634,7 +1631,7 @@ void tcpiiu::subscriptionUpdateRequest (
     minder.commit ();
 }
 
-void tcpiiu::subscriptionCancelRequest ( epicsGuard < epicsMutex > & guard, // X aCC 431
+void tcpiiu::subscriptionCancelRequest ( epicsGuard < epicsMutex > & guard,
                              nciu & chan, netSubscription & subscr )
 {
     guard.assertIdenticalMutex ( this->mutex );
@@ -2052,7 +2049,7 @@ bool tcpiiu::bytesArePendingInOS () const
     return false;
 #else
     osiSockIoctl_t bytesPending = 0; /* shut up purifys yapping */
-    int status = socket_ioctl ( this->sock, // X aCC 392
+    int status = socket_ioctl ( this->sock,
                             FIONREAD, & bytesPending );
     if ( status >= 0 ) {
         if ( bytesPending > 0 ) {
diff --git a/src/ca/test_event.cpp b/src/ca/test_event.cpp
index c39375aef..17cfe2f47 100644
--- a/src/ca/test_event.cpp
+++ b/src/ca/test_event.cpp
@@ -78,7 +78,7 @@ extern "C" void epicsShareAPI ca_dump_dbr (
         dbr_short_t *pvalue = (dbr_short_t *)pbuffer;
         for (i = 0; i < count; i++,pvalue++){
             if(count!=1 && (i%10 == 0)) printf("\n");
-            printf("%d ",* (short *)pvalue); // X aCC 392
+            printf("%d ",* (short *)pvalue);
         }
         break;
     }
@@ -96,7 +96,7 @@ extern "C" void epicsShareAPI ca_dump_dbr (
         dbr_float_t *pvalue = (dbr_float_t *)pbuffer;
         for (i = 0; i < count; i++,pvalue++){
             if(count!=1 && (i%10 == 0)) printf("\n");
-            printf("%6.4f ",*(float *)pvalue); // X aCC 392
+            printf("%6.4f ",*(float *)pvalue);
         }
         break;
     }
diff --git a/src/ca/udpiiu.cpp b/src/ca/udpiiu.cpp
index 4760583e9..e4e8bd31f 100644
--- a/src/ca/udpiiu.cpp
+++ b/src/ca/udpiiu.cpp
@@ -201,7 +201,7 @@ udpiiu::udpiiu (
     memset ( (char *)&addr, 0 , sizeof (addr) );
     addr.ia.sin_family = AF_INET;
     addr.ia.sin_addr.s_addr = htonl ( INADDR_ANY ); 
-    addr.ia.sin_port = htons ( PORT_ANY ); // X aCC 818
+    addr.ia.sin_port = htons ( PORT_ANY );
     status = bind (this->sock, &addr.sa, sizeof (addr) );
     if ( status < 0 ) {
         char sockErrBuf[64];
@@ -471,7 +471,7 @@ void epicsShareAPI caRepeaterRegistrationMessage (
     }
 
     memset ( (char *) &msg, 0, sizeof (msg) );
-    AlignedWireRef < epicsUInt16 > ( msg.m_cmmd ) = REPEATER_REGISTER; // X aCC 818
+    AlignedWireRef < epicsUInt16 > ( msg.m_cmmd ) = REPEATER_REGISTER;
     msg.m_available = saddr.ia.sin_addr.s_addr;
 
     /*
diff --git a/src/ca/virtualCircuit.h b/src/ca/virtualCircuit.h
index 3d3031f31..017b99d0e 100644
--- a/src/ca/virtualCircuit.h
+++ b/src/ca/virtualCircuit.h
@@ -335,7 +335,6 @@ private:
 
 	tcpiiu ( const tcpiiu & );
 	tcpiiu & operator = ( const tcpiiu & );
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
@@ -372,7 +371,7 @@ inline bool tcpiiu::ca_v49_ok (
 }
 
 inline bool tcpiiu::alive (
-    epicsGuard < epicsMutex > & ) const // X aCC 361
+    epicsGuard < epicsMutex > & ) const
 {
     return ( this->state == iiucs_connecting || 
         this->state == iiucs_connected );
diff --git a/src/db/dbCAC.h b/src/db/dbCAC.h
index 3032023dc..a45bc60aa 100644
--- a/src/db/dbCAC.h
+++ b/src/db/dbCAC.h
@@ -62,7 +62,7 @@ class dbChannelIO;
 class dbPutNotifyBlocker;
 class dbSubscriptionIO;
 
-class dbBaseIO                  //  X aCC 655
+class dbBaseIO
     : public chronIntIdRes < dbBaseIO > {
 public:
     virtual dbSubscriptionIO * isSubscription () = 0;
@@ -86,9 +86,9 @@ public:
         epicsGuard < epicsMutex > &, epicsMutex &,
         dbContext &, dbChannelIO &, struct dbAddr &, cacStateNotify &, 
         unsigned type, unsigned long count, unsigned mask, dbEventCtx );
-    void destructor ( epicsGuard < epicsMutex > & );
-    void unsubscribe ( epicsGuard < epicsMutex > & );
-    void channelDeleteException ( epicsGuard < epicsMutex > & );
+    void destructor ( CallbackGuard &, epicsGuard < epicsMutex > & );
+    void unsubscribe ( CallbackGuard &, epicsGuard < epicsMutex > & );
+    void channelDeleteException ( CallbackGuard &, epicsGuard < epicsMutex > & );
     void show ( epicsGuard < epicsMutex > &, unsigned level ) const;
     void show ( unsigned level ) const;
     void * operator new ( size_t size, 
@@ -110,7 +110,6 @@ private:
     dbSubscriptionIO ( const dbSubscriptionIO & );
     dbSubscriptionIO & operator = ( const dbSubscriptionIO & );
     virtual ~dbSubscriptionIO ();
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
@@ -165,7 +164,7 @@ public:
     dbContext ( epicsMutex & cbMutex, epicsMutex & mutex, 
         cacContextNotify & notify );
     virtual ~dbContext ();
-    void destroyChannel ( epicsGuard < epicsMutex > &, dbChannelIO & );
+    void destroyChannel ( CallbackGuard &,epicsGuard < epicsMutex > &, dbChannelIO & );
     void callReadNotify ( epicsGuard < epicsMutex > &, 
             struct dbAddr & addr, unsigned type, unsigned long count, 
             cacReadNotify & notify );
@@ -182,9 +181,9 @@ public:
             cacWriteNotify & notify, cacChannel::ioid * pId ); 
     void show ( unsigned level ) const;
     void showAllIO ( const dbChannelIO & chan, unsigned level ) const;
-    void destroyAllIO ( 
+    void destroyAllIO ( CallbackGuard & cbGuard,
         epicsGuard < epicsMutex > &, dbChannelIO & chan );
-    void ioCancel ( epicsGuard < epicsMutex > &, 
+    void ioCancel ( CallbackGuard &, epicsGuard < epicsMutex > &,
         dbChannelIO & chan, const cacChannel::ioid &id );
     void ioShow ( epicsGuard < epicsMutex > &,
         const cacChannel::ioid & id, unsigned level ) const;
diff --git a/src/db/dbChannelIO.cpp b/src/db/dbChannelIO.cpp
index c95778abe..294c13d71 100644
--- a/src/db/dbChannelIO.cpp
+++ b/src/db/dbChannelIO.cpp
@@ -61,19 +61,21 @@ dbChannelIO::~dbChannelIO ()
 {
 }
 
-void dbChannelIO::destructor ( epicsGuard < epicsMutex > & guard )
+void dbChannelIO::destructor ( CallbackGuard & cbGuard, 
+                              epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
-    this->serviceIO.destroyAllIO ( guard, *this );
+    this->serviceIO.destroyAllIO ( cbGuard, guard, *this );
     this->~dbChannelIO ();
 }
 
 void dbChannelIO::destroy ( 
+    CallbackGuard & cbGuard,
     epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
-    this->serviceIO.destroyChannel ( guard, *this );
-    // dont access this pointer after above call because
+    this->serviceIO.destroyChannel ( cbGuard, guard, *this );
+    // don't access this pointer after above call because
     // object nolonger exists
 }
 
@@ -132,11 +134,12 @@ void dbChannelIO::subscribe (
 }
 
 void dbChannelIO::ioCancel ( 
+    CallbackGuard & cbGuard,
     epicsGuard < epicsMutex > & mutualExclusionGuard,
     const ioid & id )
 {
     mutualExclusionGuard.assertIdenticalMutex ( this->mutex );
-    this->serviceIO.ioCancel ( mutualExclusionGuard, *this, id );
+    this->serviceIO.ioCancel ( cbGuard, mutualExclusionGuard, *this, id );
 }
 
 void dbChannelIO::ioShow ( 
@@ -204,13 +207,6 @@ void * dbChannelIO::operator new ( size_t size,
     return freeList.allocate ( size );
 }
 
-void * dbChannelIO::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 #ifdef CXX_PLACEMENT_DELETE
 void dbChannelIO::operator delete ( void *pCadaver, 
     tsFreeList < dbChannelIO, 256, epicsMutexNOOP > & freeList )
diff --git a/src/db/dbChannelIO.h b/src/db/dbChannelIO.h
index 0473962ba..54b2e2a3c 100644
--- a/src/db/dbChannelIO.h
+++ b/src/db/dbChannelIO.h
@@ -48,8 +48,10 @@ public:
         epicsMutex &, cacChannelNotify &, 
         const dbAddr &, dbContext & );
     void destructor ( 
+        CallbackGuard &,
         epicsGuard < epicsMutex > & );
     void destroy (
+        CallbackGuard &,
         epicsGuard < epicsMutex > & mutualExclusionGuard );
     void callReadNotify ( 
         epicsGuard < epicsMutex > &, 
@@ -100,7 +102,8 @@ private:
         unsigned type, unsigned long count, 
         unsigned mask, cacStateNotify &notify, ioid * );
     void ioCancel ( 
-        epicsGuard < epicsMutex > & mutualExclusionGuard,
+        CallbackGuard &,
+        epicsGuard < epicsMutex > &,
         const ioid & );
     void ioShow ( 
         epicsGuard < epicsMutex > &,
@@ -111,7 +114,6 @@ private:
         epicsGuard < epicsMutex > & ) const;
 	dbChannelIO ( const dbChannelIO & );
 	dbChannelIO & operator = ( const dbChannelIO & );
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
diff --git a/src/db/dbContext.cpp b/src/db/dbContext.cpp
index 86ebf1997..3ac05dfbc 100644
--- a/src/db/dbContext.cpp
+++ b/src/db/dbContext.cpp
@@ -83,7 +83,7 @@ dbContext::~dbContext ()
     }
 }
 
-cacChannel & dbContext::createChannel ( // X aCC 361
+cacChannel & dbContext::createChannel (
     epicsGuard < epicsMutex > & guard, const char * pName, 
     cacChannelNotify & notifyIn, cacChannel::priLev priority )
 {
@@ -119,18 +119,20 @@ cacChannel & dbContext::createChannel ( // X aCC 361
 }
 
 void dbContext::destroyChannel ( 
-    epicsGuard < epicsMutex > & guard, dbChannelIO & chan )
+                  CallbackGuard & cbGuard,
+                  epicsGuard < epicsMutex > & guard, 
+                  dbChannelIO & chan )
 {
     guard.assertIdenticalMutex ( this->mutex );
 
     if ( chan.dbContextPrivateListOfIO::pBlocker ) {
         this->ioTable.remove ( *chan.dbContextPrivateListOfIO::pBlocker );
-        chan.dbContextPrivateListOfIO::pBlocker->destructor ( guard );
+        chan.dbContextPrivateListOfIO::pBlocker->destructor ( cbGuard, guard );
         this->dbPutNotifyBlockerFreeList.release ( chan.dbContextPrivateListOfIO::pBlocker );
         chan.dbContextPrivateListOfIO::pBlocker = 0;
     }
 
-    chan.destructor ( guard );
+    chan.destructor ( cbGuard, guard );
     this->dbChannelIOFreeList.release ( & chan );
 }
 
@@ -269,7 +271,9 @@ void dbContext::initiatePutNotify (
 }
 
 void dbContext::destroyAllIO ( 
-    epicsGuard < epicsMutex > & guard, dbChannelIO & chan )
+                  CallbackGuard & cbGuard,
+                  epicsGuard < epicsMutex > & guard, 
+                  dbChannelIO & chan )
 {
     guard.assertIdenticalMutex ( this->mutex );
     dbSubscriptionIO * pIO;
@@ -286,24 +290,24 @@ void dbContext::destroyAllIO (
     while ( ( pIO = tmp.get() ) ) {
         // This prevents a db event callback from coming 
         // through after the notify IO is deleted
-        pIO->unsubscribe ( guard );
+        pIO->unsubscribe ( cbGuard, guard );
         // If they call ioCancel() here it will be ignored
         // because the IO has been unregistered above.
-        pIO->channelDeleteException ( guard );
-        pIO->destructor ( guard );
+        pIO->channelDeleteException ( cbGuard, guard );
+        pIO->destructor ( cbGuard, guard );
         this->dbSubscriptionIOFreeList.release ( pIO );
     }
 
     if ( chan.dbContextPrivateListOfIO::pBlocker ) {
-        chan.dbContextPrivateListOfIO::pBlocker->destructor ( guard );
+        chan.dbContextPrivateListOfIO::pBlocker->destructor ( cbGuard, guard );
         this->dbPutNotifyBlockerFreeList.release ( chan.dbContextPrivateListOfIO::pBlocker );
         chan.dbContextPrivateListOfIO::pBlocker = 0;
     }
 }
 
 void dbContext::ioCancel ( 
-    epicsGuard < epicsMutex > & guard, dbChannelIO & chan, 
-    const cacChannel::ioid &id )
+    CallbackGuard & cbGuard, epicsGuard < epicsMutex > & guard, 
+    dbChannelIO & chan, const cacChannel::ioid &id )
 {
     guard.assertIdenticalMutex ( this->mutex );
     dbBaseIO * pIO = this->ioTable.remove ( id );
@@ -311,13 +315,13 @@ void dbContext::ioCancel (
         dbSubscriptionIO *pSIO = pIO->isSubscription ();
         if ( pSIO ) {
             chan.dbContextPrivateListOfIO::eventq.remove ( *pSIO );
-            pSIO->unsubscribe ( guard );
-            pSIO->channelDeleteException ( guard );
-            pSIO->destructor ( guard );
+            pSIO->unsubscribe ( cbGuard, guard );
+            pSIO->channelDeleteException ( cbGuard, guard );
+            pSIO->destructor ( cbGuard, guard );
             this->dbSubscriptionIOFreeList.release ( pSIO );
         }
         else if ( pIO == chan.dbContextPrivateListOfIO::pBlocker ) {
-            chan.dbContextPrivateListOfIO::pBlocker->cancel ( guard );
+            chan.dbContextPrivateListOfIO::pBlocker->cancel ( cbGuard, guard );
         }
         else {
             errlogPrintf ( "dbContext::ioCancel() unrecognized IO was probably leaked or not canceled\n" );
diff --git a/src/db/dbPutNotifyBlocker.cpp b/src/db/dbPutNotifyBlocker.cpp
index e91234b67..6c82e4153 100644
--- a/src/db/dbPutNotifyBlocker.cpp
+++ b/src/db/dbPutNotifyBlocker.cpp
@@ -59,10 +59,11 @@ dbPutNotifyBlocker::~dbPutNotifyBlocker ()
 {
 }
 
-void dbPutNotifyBlocker::destructor ( epicsGuard < epicsMutex > & guard )
+void dbPutNotifyBlocker::destructor ( CallbackGuard & cbGuard, 
+                                  epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
-    this->cancel ( guard );
+    this->cancel ( cbGuard, guard );
     if ( this->maxValueSize > sizeof ( this->dbrScalarValue ) ) {
         char * pBuf = static_cast < char * > ( this->pn.pbuffer );
         delete [] pBuf;
@@ -71,6 +72,7 @@ void dbPutNotifyBlocker::destructor ( epicsGuard < epicsMutex > & guard )
 }
 
 void dbPutNotifyBlocker::cancel ( 
+    CallbackGuard & cbGuard,
     epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
@@ -212,13 +214,6 @@ void * dbPutNotifyBlocker::operator new ( size_t size,
     return freeList.allocate ( size );
 }
 
-void * dbPutNotifyBlocker::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 #ifdef CXX_PLACEMENT_DELETE
 void dbPutNotifyBlocker::operator delete ( void *pCadaver, 
     tsFreeList < dbPutNotifyBlocker, 64, epicsMutexNOOP > & freeList )
diff --git a/src/db/dbPutNotifyBlocker.h b/src/db/dbPutNotifyBlocker.h
index da2cc9fcb..56d3a37da 100644
--- a/src/db/dbPutNotifyBlocker.h
+++ b/src/db/dbPutNotifyBlocker.h
@@ -42,11 +42,11 @@
 class dbPutNotifyBlocker : public dbBaseIO {
 public:
     dbPutNotifyBlocker ( epicsMutex & );
-    void destructor ( epicsGuard < epicsMutex > & );
+    void destructor ( CallbackGuard &, epicsGuard < epicsMutex > & );
     void initiatePutNotify ( epicsGuard < epicsMutex > &, 
             cacWriteNotify &, struct dbAddr &, 
             unsigned type, unsigned long count, const void * pValue );
-    void cancel ( epicsGuard < epicsMutex > & );
+    void cancel ( CallbackGuard &, epicsGuard < epicsMutex > & );
     void show ( epicsGuard < epicsMutex > &, unsigned level ) const;
     void show ( unsigned level ) const;
     void * operator new ( size_t size, 
@@ -82,7 +82,6 @@ private:
 	dbPutNotifyBlocker ( const dbPutNotifyBlocker & );
 	dbPutNotifyBlocker & operator = ( const dbPutNotifyBlocker & );
     virtual ~dbPutNotifyBlocker ();
-    void * operator new ( size_t size );
     void operator delete ( void * );
 };
 
diff --git a/src/db/dbSubscriptionIO.cpp b/src/db/dbSubscriptionIO.cpp
index 4fd190d3f..260d26e89 100644
--- a/src/db/dbSubscriptionIO.cpp
+++ b/src/db/dbSubscriptionIO.cpp
@@ -66,13 +66,14 @@ dbSubscriptionIO::~dbSubscriptionIO ()
 {
 }
 
-void dbSubscriptionIO::destructor ( epicsGuard < epicsMutex > & guard )
+void dbSubscriptionIO::destructor ( CallbackGuard & cbGuard, 
+                              epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
     this->~dbSubscriptionIO ();
 }
 
-void dbSubscriptionIO::unsubscribe ( 
+void dbSubscriptionIO::unsubscribe ( CallbackGuard & cbGuard, 
     epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
@@ -87,6 +88,7 @@ void dbSubscriptionIO::unsubscribe (
 }
 
 void dbSubscriptionIO::channelDeleteException ( 
+    CallbackGuard &,
     epicsGuard < epicsMutex > & guard )
 {
     guard.assertIdenticalMutex ( this->mutex );
@@ -94,13 +96,6 @@ void dbSubscriptionIO::channelDeleteException (
         this->chan.pName(guard), this->type, this->count );
 }
 
-void * dbSubscriptionIO::operator new ( size_t ) // X aCC 361
-{
-    // The HPUX compiler seems to require this even though no code
-    // calls it directly
-    throw std::logic_error ( "why is the compiler calling private operator new" );
-}
-
 void dbSubscriptionIO::operator delete ( void * )
 {
     // Visual C++ .net appears to require operator delete if