diff --git a/examples/getme.cpp b/examples/getme.cpp
index 21f19cb..fdf2632 100644
--- a/examples/getme.cpp
+++ b/examples/getme.cpp
@@ -114,7 +114,7 @@ int main(int argc, char *argv[]) {
                 std::cout<<"Usage: "<<argv[0]<<" [-p <provider>] [-w <timeout>] [-R] <pvname> ...\n";
                 return 0;
             default:
-                std::cerr<<"Unknown argument: "<<opt<<"\n";
+                std::cerr<<"Unknown argument: "<<(int)opt<<"\n";
                 return -1;
             }
         }
diff --git a/examples/monitorme.cpp b/examples/monitorme.cpp
index 14c8419..a4dc199 100644
--- a/examples/monitorme.cpp
+++ b/examples/monitorme.cpp
@@ -175,6 +175,8 @@ struct MonTracker : public pvac::ClientChannel::MonitorCallback,
             if(n==2) {
                 // too many updates, re-queue to balance with others
                 monwork.push(shared_from_this(), evt);
+            } else if(n==0) {
+                std::cerr<<"Spurious Data event "<<name<<"\n";
             }
         }
             break;
@@ -212,7 +214,7 @@ int main(int argc, char *argv[]) {
                 std::cout<<"Usage: "<<argv[0]<<" [-p <provider>] [-w <timeout>] [-r <request>] [-R] <pvname> ...\n";
                 return 0;
             default:
-                std::cerr<<"Unknown argument: "<<opt<<"\n";
+                std::cerr<<"Unknown argument: "<<(char)opt<<"\n";
                 return -1;
             }
         }
diff --git a/examples/spamme.cpp b/examples/spamme.cpp
index c225224..6c37e2e 100644
--- a/examples/spamme.cpp
+++ b/examples/spamme.cpp
@@ -41,6 +41,7 @@ void alldone(int num)
 #endif
 
 pvd::Structure::const_shared_pointer spamtype(pvd::getFieldCreate()->createFieldBuilder()
+                                              ->setId("epics:nt/NTScalar:1.0")
                                               ->add("value", pvd::pvInt)
                                               ->createStructure());
 
diff --git a/pvtoolsSrc/pvput.cpp b/pvtoolsSrc/pvput.cpp
index 8a36926..db5ae9a 100644
--- a/pvtoolsSrc/pvput.cpp
+++ b/pvtoolsSrc/pvput.cpp
@@ -269,6 +269,8 @@ struct Putter : public pvac::ClientChannel::PutCallback
 
     shared_vector<std::string> jarr;
 
+    PVStructure::const_shared_pointer current;
+
     virtual void putBuild(const epics::pvData::StructureConstPtr& build, Args& args)
     {
         if(debug) std::cerr<<"Server defined structure\n"<<build;
@@ -314,13 +316,14 @@ struct Putter : public pvac::ClientChannel::PutCallback
                 PVStructure* sfld(static_cast<PVStructure*>(fld.get()));
 
                 PVScalar* idxfld(sfld->getSubFieldT<PVScalar>("index").get());
-                PVStringArray::const_svector choices(sfld->getSubFieldT<PVStringArray>("choices")->view());
+                PVStringArray::const_svector choices(current->getSubFieldT<PVStringArray>("value.choices")->view());
 
                 bool found=false;
                 for(size_t i=0; i<choices.size(); i++) {
                     if(bare[0]==choices[i]) {
                         idxfld->putFrom<int64>(i);
                         found=true;
+                        break;
                     }
                 }
 
@@ -615,9 +618,11 @@ int main (int argc, char *argv[])
 
     pvac::ClientChannel chan(ctxt.connect(pvName));
 
+    thework.current = chan.get(timeOut, pvRequest);
+
     if (mode != TerseMode && !quiet) {
         std::cout << "Old : ";
-        printValue(pvName, chan.get(timeOut, pvRequest));
+        printValue(pvName, thework.current);
     }
 
     {
diff --git a/src/client/clientMonitor.cpp b/src/client/clientMonitor.cpp
index 2a7c321..8b7debd 100644
--- a/src/client/clientMonitor.cpp
+++ b/src/client/clientMonitor.cpp
@@ -196,16 +196,29 @@ bool Monitor::poll()
     Guard G(impl->mutex);
 
     if(!impl->done && impl->last.next()) {
-        root = impl->last->pvStructurePtr;
+        const epics::pvData::PVStructurePtr& ptr = impl->last->pvStructurePtr;
         changed = *impl->last->changedBitSet;
         overrun = *impl->last->overrunBitSet;
 
+        /* copy the exposed PVStructure for two reasons.
+         * 1. Prevent accidental use of shared container after release()
+         * 2. Allows caller to cache results of getSubField() until root.get() changes.
+         */
+        if(!root || (void*)root->getField().get()!=(void*)ptr->getField().get()) {
+            // initial connection, or new type
+            root = pvd::getPVDataCreate()->createPVStructure(ptr); // also calls copyUnchecked()
+        } else {
+            // same type
+            const_cast<pvd::PVStructure&>(*root).copyUnchecked(*ptr, changed);
+        }
+
+        impl->seenEmpty = false;
     } else {
-        root.reset();
         changed.clear();
         overrun.clear();
+        impl->seenEmpty = true;
     }
-    return impl->seenEmpty = !!root;
+    return !impl->seenEmpty;
 }
 
 bool Monitor::complete() const
diff --git a/src/client/pva/client.h b/src/client/pva/client.h
index e9b6897..21f6b3a 100644
--- a/src/client/pva/client.h
+++ b/src/client/pva/client.h
@@ -104,13 +104,31 @@ struct epicsShareClass Monitor
     void cancel();
     /** updates root, changed, overrun
      *
-     * @return true if root!=NULL
+     * @return true if a new update was extracted from the queue.
+     * @note This method does not block.
      * @note MonitorEvent::Data will not be repeated until poll()==false.
+     * @post root!=NULL (after version 6.0.0)
+     * @post root!=NULL iff poll()==true  (In version 6.0.0)
      */
     bool poll();
     //! true if all events received.
     //! Check after poll()==false
     bool complete() const;
+    /** Monitor update data.
+     *
+     * After version 6.0.0
+     *
+     * Initially NULL, becomes !NULL the first time poll()==true.
+     * The PVStructure pointed to be root will presist until
+     * Monitor reconnect w/ type change.  This can be detected
+     * by comparing `root.get()`.  references to root may be cached
+     * subject to this test.
+     *
+     * In version 6.0.0
+     *
+     * NULL except after poll()==true.  poll()==false sets root=NULL.
+     * references to root should not be stored between calls to poll().
+     */
     epics::pvData::PVStructure::const_shared_pointer root;
     epics::pvData::BitSet changed,
                           overrun;
diff --git a/src/ioc/PVAServerRegister.cpp b/src/ioc/PVAServerRegister.cpp
index 6360914..fbee91f 100644
--- a/src/ioc/PVAServerRegister.cpp
+++ b/src/ioc/PVAServerRegister.cpp
@@ -46,7 +46,7 @@ void startitup() {
     the_server = pva::ServerContext::create(pva::ServerContext::Config()
                                             .config(pva::ConfigurationBuilder()
                                                     // default to all providers instead of just "local"
-                                                    .add("EPICS_PVAS_PROVIDER_NAMES", PVACCESS_ALL_PROVIDERS)
+                                                    .add("EPICS_PVAS_PROVIDER_NAMES", pva::PVACCESS_ALL_PROVIDERS)
                                                     .push_map()
                                                     // prefer to use EPICS_PVAS_PROVIDER_NAMES
                                                     // from environment
diff --git a/src/pva/pv/pvaConstants.h b/src/pva/pv/pvaConstants.h
index 408d96f..9ee652d 100644
--- a/src/pva/pv/pvaConstants.h
+++ b/src/pva/pv/pvaConstants.h
@@ -67,19 +67,19 @@ const epics::pvData::int16 PVA_DEFAULT_PRIORITY = 0;
 const epics::pvData::uint32 MAX_CHANNEL_NAME_LENGTH = 500;
 
 /** Invalid data type. */
-const epics::pvData::int16 INVALID_DATA_TYPE = static_cast<epics::pvData::int16>(0xFFFF);
+const epics::pvData::int16 INVALID_DATA_TYPE = 0xFFFF;
 
 /** Invalid IOID. */
 const epics::pvData::int32 INVALID_IOID = 0;
 
 /** Default PVA provider name. */
-#define PVACCESS_DEFAULT_PROVIDER "local"
+const std::string PVACCESS_DEFAULT_PROVIDER;
 
 /** "All-providers registered" PVA provider name. */
-#define PVACCESS_ALL_PROVIDERS "<all>"
+const std::string PVACCESS_ALL_PROVIDERS;
 
 /** Name of the system env. variable to turn on debugging. */
-#define PVACCESS_DEBUG "EPICS_PVA_DEBUG"
+const std::string PVACCESS_DEBUG;
 }
 }
 
diff --git a/src/pva/pvaVersion.cpp b/src/pva/pvaVersion.cpp
index b925442..f196242 100644
--- a/src/pva/pvaVersion.cpp
+++ b/src/pva/pvaVersion.cpp
@@ -15,6 +15,10 @@ using std::string;
 namespace epics {
 namespace pvAccess {
 
+const std::string PVACCESS_DEFAULT_PROVIDER = "local";
+const std::string PVACCESS_ALL_PROVIDERS = "<all>";
+const std::string PVACCESS_DEBUG = "EPICS_PVA_DEBUG";
+
 Version::Version(std::string const & productName,
                  std::string const & implementationLangugage,
                  int majorVersion, int minorVersion,
diff --git a/src/remote/codec.cpp b/src/remote/codec.cpp
index 3ed6b93..cd45e83 100644
--- a/src/remote/codec.cpp
+++ b/src/remote/codec.cpp
@@ -337,7 +337,7 @@ void AbstractCodec::processReadSegmented() {
                     " %s:%d: %s, disconnecting...",
                     __FILE__, __LINE__, inetAddressToString(*getLastReadBufferSocketAddress()).c_str());
                 invalidDataStreamHandler();
-                throw new invalid_data_stream_exception(
+                throw invalid_data_stream_exception(
                     "not-a-first segmented message expected");
             }
 
@@ -1586,11 +1586,11 @@ void BlockingServerTCPTransportCodec::destroyAllChannels() {
             _socketName.c_str(), _channels.size());
     }
 
-    std::map<pvAccessID, ServerChannel::shared_pointer>::iterator it = _channels.begin();
-    for(; it!=_channels.end(); it++)
-        it->second->destroy();
+    _channels_t temp;
+    temp.swap(_channels);
 
-    _channels.clear();
+    for(_channels_t::iterator it(temp.begin()), end(temp.end()); it!=end; ++it)
+        it->second->destroy();
 }
 
 void BlockingServerTCPTransportCodec::internalClose(bool force) {
diff --git a/src/remote/transportRegistry.cpp b/src/remote/transportRegistry.cpp
index 62dfb45..952a0fa 100644
--- a/src/remote/transportRegistry.cpp
+++ b/src/remote/transportRegistry.cpp
@@ -74,28 +74,6 @@ TransportRegistry::~TransportRegistry()
     if(!transports.empty())
         LOG(logLevelWarn, "TransportRegistry destroyed while not empty");
 }
-/*
-void
-TransportRegistry::get(const osiSockAddr* address, transportVector_t& output)
-{
-    pvd::Lock guard(_mutex);
-    transportsMap_t::iterator transportsIter = _transports.find(address);
-    if(transportsIter != _transports.end())
-    {
-        prioritiesMapSharedPtr_t& priorities = transportsIter->second;
-
-        size_t i = output.size();
-        output.resize(output.size() + priorities->size());
-
-        for(prioritiesMap_t::iterator prioritiesIter = priorities->begin();
-                prioritiesIter != priorities->end();
-                prioritiesIter++, i++)
-        {
-            output[i] = prioritiesIter->second;
-        }
-    }
-}
-*/
 
 Transport::shared_pointer TransportRegistry::get(const osiSockAddr& address, epics::pvData::int16 prio)
 {
@@ -124,19 +102,14 @@ void TransportRegistry::install(const Transport::shared_pointer& ptr)
 Transport::shared_pointer TransportRegistry::remove(Transport::shared_pointer const & transport)
 {
     assert(!!transport);
+    const Key key(transport->getRemoteAddress(), transport->getPriority());
     Transport::shared_pointer ret;
 
     pvd::Lock guard(_mutex);
-    for(transports_t::iterator it(transports.begin()), end(transports.end());
-        it != end; ++it)
-    {
-        Transport::shared_pointer& tr = it->second;
-
-        if(transport.get() == tr.get()) {
-            ret.swap(it->second);
-            transports.erase(it);
-            break;
-        }
+    transports_t::iterator it(transports.find(key));
+    if(it!=transports.end()) {
+        ret.swap(it->second);
+        transports.erase(it);
     }
     return ret;
 }
diff --git a/src/remoteClient/clientContextImpl.cpp b/src/remoteClient/clientContextImpl.cpp
index 3800503..18ce6b1 100644
--- a/src/remoteClient/clientContextImpl.cpp
+++ b/src/remoteClient/clientContextImpl.cpp
@@ -3828,7 +3828,9 @@ public:
                     for(size_t i=0, N=ops.size(); i<N; i++) {
                         ResponseRequest::shared_pointer R(ops[i].lock());
                         if(!R) continue;
-                        EXCEPTION_GUARD(R->getRequester()->channelDisconnect(connectionState==Channel::DESTROYED);)
+                        ChannelBaseRequester::shared_pointer req(R->getRequester());
+                        if(!req) continue;
+                        EXCEPTION_GUARD(req->channelDisconnect(connectionState==Channel::DESTROYED);)
                     }
                 }
             }
diff --git a/src/server/responseHandlers.cpp b/src/server/responseHandlers.cpp
index f666994..8267292 100644
--- a/src/server/responseHandlers.cpp
+++ b/src/server/responseHandlers.cpp
@@ -2035,7 +2035,7 @@ void ServerMonitorRequesterImpl::destroy()
 
     // hold a reference to channelMonitor so that _channelMonitor.reset()
     // does not call ~Monitor (external code) while we are holding a lock
-    Monitor::shared_pointer monitor = _channelMonitor;
+    Monitor::shared_pointer monitor(_channelMonitor);
     {
         Lock guard(_mutex);
         _channel->unregisterRequest(_ioid);
diff --git a/src/server/serverContext.cpp b/src/server/serverContext.cpp
index 3d7a969..3ba9364 100644
--- a/src/server/serverContext.cpp
+++ b/src/server/serverContext.cpp
@@ -362,13 +362,6 @@ void ServerContextImpl::shutdown()
 
 void ServerContextImpl::destroyAllTransports()
 {
-    TransportRegistry::transportVector_t transports;
-    _transportRegistry.toArray(transports);
-
-    size_t size = transports.size();
-    if (size == 0)
-        return;
-
     // now clear all (release)
     _transportRegistry.clear();
 }
diff --git a/src/utils/pv/fairQueue.h b/src/utils/pv/fairQueue.h
index b3c30df..20447ff 100644
--- a/src/utils/pv/fairQueue.h
+++ b/src/utils/pv/fairQueue.h
@@ -72,9 +72,7 @@ public:
         } enode;
         unsigned Qcnt;
         value_type holder;
-#ifndef NDEBUG
         fair_queue *owner;
-#endif
 
         friend class fair_queue;
 
@@ -82,9 +80,7 @@ public:
         entry& operator=(const entry&);
     public:
         entry() :Qcnt(0), holder()
-#ifndef NDEBUG
             , owner(NULL)
-#endif
         {
             enode.node.next = enode.node.previous = NULL;
             enode.self = this;
@@ -92,9 +88,8 @@ public:
         ~entry() {
             // nodes should be removed from the list before deletion
             assert(!enode.node.next && !enode.node.previous);
-#ifndef NDEBUG
+            assert(Qcnt==0 && !holder);
             assert(!owner);
-#endif
         }
     };
 
@@ -144,6 +139,7 @@ public:
 
     bool pop_front_try(value_type& ret)
     {
+        ret.reset();
         guard_t G(mutex);
         ELLNODE *cur = ellGet(&list); // pop_front
 
@@ -165,7 +161,6 @@ public:
             }
             return true;
         } else {
-            ret.reset();
             return false;
         }
     }