diff --git a/src/ca/udpiiu.cpp b/src/ca/udpiiu.cpp
index 53e7896fd..fb073210d 100644
--- a/src/ca/udpiiu.cpp
+++ b/src/ca/udpiiu.cpp
@@ -1223,11 +1223,16 @@ void udpiiu::flushRequest (
     netiiu::flushRequest ( guard );
 }
 
-void udpiiu::eliminateExcessiveSendBacklog ( 
-    epicsGuard < epicsMutex > * pCBGuard,
+unsigned udpiiu::requestMessageBytesPending ( 
     epicsGuard < epicsMutex > & guard )
 {
-    netiiu::eliminateExcessiveSendBacklog ( pCBGuard, guard );
+    return netiiu::requestMessageBytesPending ( guard );
+}
+
+void udpiiu::flush ( 
+    epicsGuard < epicsMutex > & guard )
+{
+    netiiu::flush ( guard );
 }
 
 void udpiiu::requestRecvProcessPostponedFlush (
diff --git a/src/ca/udpiiu.h b/src/ca/udpiiu.h
index 0f9b191d1..29ed08faf 100644
--- a/src/ca/udpiiu.h
+++ b/src/ca/udpiiu.h
@@ -189,8 +189,9 @@ private:
         epicsGuard < epicsMutex > & ) const;
     bool ca_v42_ok (
         epicsGuard < epicsMutex > & ) const;
-    void eliminateExcessiveSendBacklog ( 
-        epicsGuard < epicsMutex > * pCallbackGuard,
+    unsigned requestMessageBytesPending ( 
+        epicsGuard < epicsMutex > & mutualExclusionGuard );
+    void flush ( 
         epicsGuard < epicsMutex > & mutualExclusionGuard );
     void writeRequest ( 
         epicsGuard < epicsMutex > &, nciu &, 
diff --git a/src/ca/virtualCircuit.h b/src/ca/virtualCircuit.h
index 7532ce181..0530aca23 100644
--- a/src/ca/virtualCircuit.h
+++ b/src/ca/virtualCircuit.h
@@ -124,9 +124,11 @@ public:
 
     void flushRequest ( 
         epicsGuard < epicsMutex > & );
-    void eliminateExcessiveSendBacklog ( 
-        epicsGuard < epicsMutex > * pCallbackGuard,
+    unsigned requestMessageBytesPending ( 
         epicsGuard < epicsMutex > & mutualExclusionGuard );
+    void flush ( 
+        epicsGuard < epicsMutex > & mutualExclusionGuard );
+
     void show ( unsigned level ) const;
     bool setEchoRequestPending ( 
         epicsGuard < epicsMutex > & );
@@ -294,8 +296,8 @@ private:
         nciu & chan, netSubscription & subscr );
     void flushIfRecvProcessRequested (
         epicsGuard < epicsMutex > & );
-    bool flush ( 
-        epicsGuard < epicsMutex > & ); // only to be called by the send thread
+    bool sendThreadFlush ( 
+        epicsGuard < epicsMutex > & );
 
     // netiiu stubs
     void uninstallChanDueToSuccessfulSearchResponse ( 
diff --git a/src/db/dbChannelIO.cpp b/src/db/dbChannelIO.cpp
index a70e2cf7b..510921b64 100644
--- a/src/db/dbChannelIO.cpp
+++ b/src/db/dbChannelIO.cpp
@@ -69,11 +69,10 @@ void dbChannelIO::destructor ( epicsGuard < epicsMutex > & guard )
 }
 
 void dbChannelIO::destroy ( 
-    epicsGuard < epicsMutex > & /* callbackControlGuard */, 
-    epicsGuard < epicsMutex > & mutualExclusionGuard )
+    epicsGuard < epicsMutex > & guard )
 {
-    mutualExclusionGuard.assertIdenticalMutex ( this->mutex );
-    this->serviceIO.destroyChannel ( mutualExclusionGuard, *this );
+    guard.assertIdenticalMutex ( this->mutex );
+    this->serviceIO.destroyChannel ( guard, *this );
     // dont access this pointer after above call because
     // object nolonger exists
 }
@@ -133,7 +132,6 @@ void dbChannelIO::subscribe (
 }
 
 void dbChannelIO::ioCancel ( 
-    epicsGuard < epicsMutex > & /* callbackControlGuard */, 
     epicsGuard < epicsMutex > & mutualExclusionGuard,
     const ioid & id )
 {
@@ -232,9 +230,14 @@ void dbChannelIO::operator delete ( void * )
         __FILE__, __LINE__ );
 }
 
-void dbChannelIO::eliminateExcessiveSendBacklog (
-    epicsGuard < epicsMutex > * /* pCallbackGuard */, 
-    epicsGuard < epicsMutex > & /* mutualExclusionGuard */ )
+void dbChannelIO::flush (
+    epicsGuard < epicsMutex > & )
 {
 }
 
+unsigned dbChannelIO::requestMessageBytesPending (
+    epicsGuard < epicsMutex > & )
+{
+    return 0u;
+}
+
diff --git a/src/db/dbChannelIO.h b/src/db/dbChannelIO.h
index 971ec8922..557abbf13 100644
--- a/src/db/dbChannelIO.h
+++ b/src/db/dbChannelIO.h
@@ -50,7 +50,6 @@ public:
     void destructor ( 
         epicsGuard < epicsMutex > & );
     void destroy (
-        epicsGuard < epicsMutex > & callbackControlGuard, 
         epicsGuard < epicsMutex > & mutualExclusionGuard );
     void callReadNotify ( 
         epicsGuard < epicsMutex > &, 
@@ -80,9 +79,10 @@ private:
 
     void initiateConnect (
         epicsGuard < epicsMutex > & );
-    void eliminateExcessiveSendBacklog (
-        epicsGuard < epicsMutex > * pCallbackGuard, 
-        epicsGuard < epicsMutex > & mutualExclusionGuard );
+    unsigned requestMessageBytesPending ( 
+        epicsGuard < epicsMutex > & );
+    void flush ( 
+        epicsGuard < epicsMutex > & );
     ioStatus read ( 
         epicsGuard < epicsMutex > &,
         unsigned type, unsigned long count, 
@@ -100,7 +100,6 @@ private:
         unsigned type, unsigned long count, 
         unsigned mask, cacStateNotify &notify, ioid * );
     void ioCancel ( 
-        epicsGuard < epicsMutex > & callbackControlGuard, 
         epicsGuard < epicsMutex > & mutualExclusionGuard,
         const ioid & );
     void ioShow (