diff --git a/mps/code/arenacl.c b/mps/code/arenacl.c
index f6d262b6e04..2dd5564acec 100644
--- a/mps/code/arenacl.c
+++ b/mps/code/arenacl.c
@@ -305,8 +305,9 @@ static Res ClientArenaCreate(Arena *arenaReturn, ArgList args)
   arena->zoneShift = SizeFloorLog2(size >> MPS_WORD_SHIFT);
   AVER(ArenaGrainSize(arena) == ChunkPageSize(arena->primary));
 
-  EVENT6(ArenaCreateCL, arena, size, base, grainSize,
-         ClassOfPoly(Arena, arena), arena->serial);
+  EVENT7(ArenaCreateCL, arena, size, base, grainSize,
+         ClassOfPoly(Arena, arena), ArenaGlobals(arena)->systemPools,
+         arena->serial);
   AVERT(ClientArena, clientArena);
   *arenaReturn = arena;
   return ResOK;
diff --git a/mps/code/arenavm.c b/mps/code/arenavm.c
index 35224680106..d928b056539 100644
--- a/mps/code/arenavm.c
+++ b/mps/code/arenavm.c
@@ -659,8 +659,9 @@ static Res VMArenaCreate(Arena *arenaReturn, ArgList args)
   AVER(ChunkPageSize(chunk) == ArenaGrainSize(arena));
 
   AVERT(VMArena, vmArena);
-  EVENT6(ArenaCreateVM, arena, size, chunkSize, grainSize,
-         ClassOfPoly(Arena, arena), arena->serial);
+  EVENT7(ArenaCreateVM, arena, size, chunkSize, grainSize,
+         ClassOfPoly(Arena, arena), ArenaGlobals(arena)->systemPools,
+         arena->serial);
 
   vmArena->extended(arena, chunk->base, chunkSize);
   
diff --git a/mps/code/eventdef.h b/mps/code/eventdef.h
index a58599f4086..2a5ab969ffe 100644
--- a/mps/code/eventdef.h
+++ b/mps/code/eventdef.h
@@ -36,7 +36,7 @@
  */
 
 #define EVENT_VERSION_MAJOR  ((unsigned)2)
-#define EVENT_VERSION_MEDIAN ((unsigned)3)
+#define EVENT_VERSION_MEDIAN ((unsigned)4)
 #define EVENT_VERSION_MINOR  ((unsigned)0)
 
 
@@ -243,7 +243,8 @@
   PARAM(X,  2, W, chunkSize) /* arena's chunk size in bytes */ \
   PARAM(X,  3, W, grainSize) /* arena's grain size in bytes */ \
   PARAM(X,  4, P, arenaClass) /* arena's class */ \
-  PARAM(X,  5, U, serial) /* arena's serial number */
+  PARAM(X,  5, W, systemPools) /* number of system pools */ \
+  PARAM(X,  6, U, serial) /* arena's serial number */
 
 #define EVENT_ArenaWriteFaults_PARAMS(PARAM, X) \
   PARAM(X,  0, P, arena) \
@@ -287,7 +288,8 @@
   PARAM(X,  2, A, base) /* base address of memory given to arena */ \
   PARAM(X,  3, W, grainSize) /* arena's grain size in bytes */ \
   PARAM(X,  4, P, arenaClass) /* arena's class */ \
-  PARAM(X,  5, U, serial) /* arena's serial number */
+  PARAM(X,  5, W, systemPools) /* number of system pools */ \
+  PARAM(X,  6, U, serial) /* arena's serial number */
 
 #define EVENT_ArenaDestroy_PARAMS(PARAM, X) \
   PARAM(X,  0, P, arena)
diff --git a/mps/tool/monitor b/mps/tool/monitor
index e6080404c62..aed77a7a111 100755
--- a/mps/tool/monitor
+++ b/mps/tool/monitor
@@ -619,7 +619,6 @@ class Trace(EventHandler):
 
     def TraceDestroy(self, t, event):
         self.add_time("destroy", t, event)
-        self.pause_end(t, event)
 
     def TraceStatScan(self, t, event):
         self.add_count('roots scanned', event.rootScanCount)
@@ -719,16 +718,13 @@ class Trace(EventHandler):
 
 class Arena(EventHandler):
     "Model of an MPS arena."
-    # Number of pools that are internal to the arena; see the list in
-    # global.c:GlobalsPrepareToDestroy.
-    _internal_pools = 4
-
     def __init__(self, model, pointer, t):
         "Create Arena owned by model, at pointer, at time t."
         self.model = model       # Owning model.
         self._pointer = pointer  # Arena's pointer.
         self._arena_class = None # Arena's class pointer.
         self._serial = None      # Arena's serial number.
+        self._system_pools = 0   # Number of system pools.
         self._pools = []         # List of Pools ever belonging to arena.
         self._pool = {}          # Pointer -> Pool (for live pools).
         self._gens = []          # List of Gens ever belonging to arena.
@@ -795,12 +791,12 @@ class Arena(EventHandler):
 
     def ArenaAlloc(self, t, event):
         self.delegate_to_pool(t, event)
-        if self._pool[event.pool]._serial >= self._internal_pools:
+        if self._pool[event.pool]._serial >= self._system_pools:
             self._alloc.add(t, event.size)
 
     def ArenaFree(self, t, event):
         self.delegate_to_pool(t, event)
-        if self._pool[event.pool]._serial >= self._internal_pools:
+        if self._pool[event.pool]._serial >= self._system_pools:
             self._alloc.sub(t, event.size)
 
     PoolInit = \
@@ -824,6 +820,7 @@ class Arena(EventHandler):
     def ArenaCreateVM(self, t, event):
         self._arena_class = event.arenaClass
         self._serial = event.serial
+        self._system_pools = event.systemPools
 
     ArenaCreateCL = ArenaCreateVM