diff --git a/src/ca/caChannel.cpp b/src/ca/caChannel.cpp
index 66535f3..33ed880 100644
--- a/src/ca/caChannel.cpp
+++ b/src/ca/caChannel.cpp
@@ -1427,17 +1427,11 @@ CAChannelMonitor::CAChannelMonitor(CAChannel::shared_pointer const & _channel,
     monitorRequester(_monitorRequester),
     getType(getDBRType(pvRequest, _channel->getNativeType())),
     pvStructure(createPVStructure(_channel, getType, pvRequest)),
-    changedBitSet(new BitSet(static_cast<uint32>(pvStructure->getStructure()->getNumberFields()))),
-    overrunBitSet(new BitSet(static_cast<uint32>(pvStructure->getStructure()->getNumberFields()))),
     count(0),
-    element(new MonitorElement())
+    element(new MonitorElement(pvStructure))
 {
     // TODO
-    changedBitSet->set(0);
-
-    element->pvStructurePtr = pvStructure;
-    element->changedBitSet = changedBitSet;
-    element->overrunBitSet = overrunBitSet;
+    element->changedBitSet->set(0);
 }
 
 void CAChannelMonitor::activate()
diff --git a/src/client/pv/monitor.h b/src/client/pv/monitor.h
index 1cbf509..b08b0e4 100644
--- a/src/client/pv/monitor.h
+++ b/src/client/pv/monitor.h
@@ -36,17 +36,19 @@ typedef std::tr1::shared_ptr<Monitor> MonitorPtr;
  * @author mrk
  */
 class epicsShareClass MonitorElement {
-    public:
+public:
     POINTER_DEFINITIONS(MonitorElement);
     MonitorElement(){}
-    MonitorElement(epics::pvData::PVStructurePtr const & pvStructurePtr)
-    : pvStructurePtr(pvStructurePtr),
-      changedBitSet(epics::pvData::BitSet::create(static_cast<epics::pvData::uint32>(pvStructurePtr->getNumberFields()))),
-      overrunBitSet(epics::pvData::BitSet::create(static_cast<epics::pvData::uint32>(pvStructurePtr->getNumberFields())))
-    {}
-    epics::pvData::PVStructurePtr pvStructurePtr;
-    epics::pvData::BitSet::shared_pointer changedBitSet;
-    epics::pvData::BitSet::shared_pointer overrunBitSet;
+    MonitorElement(epics::pvData::PVStructurePtr const & pvStructurePtr);
+    const epics::pvData::PVStructurePtr pvStructurePtr;
+    const epics::pvData::BitSet::shared_pointer changedBitSet;
+    const epics::pvData::BitSet::shared_pointer overrunBitSet;
+    // info to assist monitor debugging
+    enum state_t {
+        Free,   //!< data invalid.  eg. on internal free list
+        Queued, //!< data valid.  Owned by Monitor.  Waiting for Monitor::poll()
+        InUse   //!< data valid.  Owned by MonitorRequester.  Waiting for Monitor::release()
+    } state;
 };
 
 /**
diff --git a/src/client/pvAccess.cpp b/src/client/pvAccess.cpp
index c24e533..e49bf05 100644
--- a/src/client/pvAccess.cpp
+++ b/src/client/pvAccess.cpp
@@ -124,5 +124,11 @@ ChannelRequester::shared_pointer DefaultChannelRequester::build()
 }
 
 
-}
-}
+MonitorElement::MonitorElement(epics::pvData::PVStructurePtr const & pvStructurePtr)
+    : pvStructurePtr(pvStructurePtr)
+    ,changedBitSet(epics::pvData::BitSet::create(static_cast<epics::pvData::uint32>(pvStructurePtr->getNumberFields())))
+    ,overrunBitSet(epics::pvData::BitSet::create(static_cast<epics::pvData::uint32>(pvStructurePtr->getNumberFields())))
+    ,state(Free)
+{}
+
+}} // namespace epics::pvAccess
diff --git a/testApp/remote/testServer.cpp b/testApp/remote/testServer.cpp
index ab46846..e663ce8 100644
--- a/testApp/remote/testServer.cpp
+++ b/testApp/remote/testServer.cpp
@@ -1926,8 +1926,6 @@ private:
     bool m_continuous;
     PVStructure::shared_pointer m_pvStructure;
     PVStructure::shared_pointer m_ccopy;
-    BitSet::shared_pointer m_changedBitSet;
-    BitSet::shared_pointer m_overrunBitSet;
     Mutex m_lock;
     enum QueueState { MM_STATE_FULL, MM_STATE_TAKEN, MM_STATE_FREE };
     QueueState m_state ;
@@ -1935,7 +1933,6 @@ private:
 
 
     MonitorElement::shared_pointer m_thisPtr;
-    MonitorElement::shared_pointer m_nullMonitor;
 
 protected:
     MockMonitor(std::string const & channelName, MonitorRequester::shared_pointer const & monitorRequester,
@@ -1945,11 +1942,9 @@ protected:
         m_continuous(false),
         m_pvStructure(getRequestedStructure(pvStructure, pvRequest)),
         m_ccopy(getPVDataCreate()->createPVStructure(m_pvStructure->getStructure())),
-        m_changedBitSet(new BitSet(m_pvStructure->getNumberFields())),
-        m_overrunBitSet(new BitSet(m_pvStructure->getNumberFields())),
         m_lock(),
         m_state(MM_STATE_FREE),
-        m_thisPtr(new MonitorElement())
+        m_thisPtr(new MonitorElement(m_ccopy))
     {
         PVACCESS_REFCOUNT_MONITOR_CONSTRUCT(mockMonitor);
 
@@ -1958,11 +1953,7 @@ protected:
             m_continuous = pvScalar->getAs<epics::pvData::boolean>();
 
         // we always send all
-        m_changedBitSet->set(0);
-
-        m_thisPtr->pvStructurePtr = m_ccopy;
-        m_thisPtr->changedBitSet = m_changedBitSet;
-        m_thisPtr->overrunBitSet = m_overrunBitSet;
+        m_thisPtr->changedBitSet->set(0);
     }
 
 public:
@@ -2034,13 +2025,13 @@ public:
 
                 if (m_state == MM_STATE_FULL || m_state == MM_STATE_TAKEN)      // "queue" full
                 {
-                    m_overrunBitSet->set(0);
+                    m_thisPtr->overrunBitSet->set(0);
                     copy();
                     return;
                 }
                 else
                 {
-                    m_overrunBitSet->clear(0);
+                    m_thisPtr->overrunBitSet->clear(0);
                     m_state = MM_STATE_FULL;
                     copy();
                 }
@@ -2058,7 +2049,7 @@ public:
         Lock xx(m_lock);
         if (m_state != MM_STATE_FULL)
         {
-            return m_nullMonitor;
+            return MonitorElement::shared_pointer();
         }
         else
         {