diff --git a/server/core/dcb.c b/server/core/dcb.c
index 01717667c..80dd84cec 100644
--- a/server/core/dcb.c
+++ b/server/core/dcb.c
@@ -56,6 +56,8 @@
  *                                      remove dcb_set_state etc, simplifications.
  * 10/07/2015   Martin Brampton         Simplify, merge dcb_read and dcb_read_n
  * 04/09/2015   Martin Brampton         Changes to ensure DCB always has session pointer
+ * 28/09/2015   Martin Brampton         Add counters, maxima for DCBs and zombies
+ * 29/05/2015   Martin Brampton         Impose locking in dcb_call_foreach callbacks
  *
  * @endverbatim
  */
@@ -87,7 +89,11 @@ extern size_t         log_ses_count[];
 extern __thread log_info_t tls_log_info;
 
 static	DCB		*allDCBs = NULL;	/* Diagnostics need a list of DCBs */
+static  int             nDCBs = 0;
+static  int             maxDCBs = 0;
 static	DCB		*zombies = NULL;
+static  int             nzombies = 0;
+static  int             maxzombies = 0;
 static	SPINLOCK	dcbspin = SPINLOCK_INIT;
 static	SPINLOCK	zombiespin = SPINLOCK_INIT;
 
@@ -227,6 +233,8 @@ DCB	*newdcb;
             ptr = ptr->next;
         ptr->next = newdcb;
     }
+    nDCBs++;
+    if (nDCBs > maxDCBs) maxDCBs = nDCBs;
     spinlock_release(&dcbspin);
     return newdcb;
 }
@@ -328,6 +336,7 @@ dcb_final_free(DCB *dcb)
 		if (ptr)
 			ptr->next = dcb->next;
 	}
+        nDCBs--;
     spinlock_release(&dcbspin);
 
     if (dcb->session) {
@@ -492,6 +501,7 @@ DCB     *listofdcb = NULL;
                                  * (listofdcb) is not NULL, then it follows that
                                  * dcb will also not be null.
 				 */
+                nzombies--;
                 zombiedcb->memdata.next = listofdcb;
                 listofdcb = zombiedcb;
 			}
@@ -565,6 +575,8 @@ dcb_process_victim_queue(DCB *listofdcb)
                     nextdcb = dcb->memdata.next;
                     dcb->memdata.next = zombies;
                     zombies = dcb;
+                    nzombies++;
+                    if (nzombies > maxzombies) maxzombies = nzombies;
                     spinlock_release(&zombiespin);
                     if (dcb->server)
                     {
@@ -1800,6 +1812,8 @@ dcb_close(DCB *dcb)
         dcb->dcb_is_zombie = true;
         dcb->memdata.next = zombies;
         zombies = dcb;
+        nzombies++;
+        if (nzombies > maxzombies) maxzombies = nzombies;
         /*< Set bit for each maxscale thread. This should be done before
 		 * the state is changed, so as to protect the DCB from premature
 		 * destruction. */
@@ -2695,17 +2709,21 @@ dcb_call_foreach(struct server* server, DCB_REASON reason)
                 case DCB_REASON_NOT_RESPONDING: 
                 {
                         DCB *dcb;
-                        dcb = dcb_get_next(NULL);
-                        
+                        spinlock_acquire(&dcbspin);
+                        dcb = allDCBs;
+
                         while (dcb != NULL)
                         {
+                                spinlock_acquire(&dcb->dcb_initlock);
                                 if (dcb->state == DCB_STATE_POLLING && dcb->server &&
-				    strcmp(dcb->server->unique_name,server->unique_name) == 0)
+                                    strcmp(dcb->server->unique_name,server->unique_name) == 0)
                                 {
                                         dcb_call_callback(dcb, DCB_REASON_NOT_RESPONDING);
                                 }
-                                dcb = dcb_get_next(dcb);
+                                spinlock_release(&dcb->dcb_initlock);
+                                dcb = dcb->next;
                         }
+                        spinlock_release(&dcbspin);
                         break;
                 }