Example 1 (queue depth events)

The queue, MYQUEUE1, has a maximum depth of 1000 messages, and the high and low queue depth limits are 80% and 20% respectively. Initially, Queue Depth High events are enabled, while the other queue depth events are disabled.

The WebSphere MQ commands (MQSC) to configure this queue are:

Figure 7. Definition of MYQUEUE1

  ALTER QMGR PERFMEV(ENABLED)
 
  DEFINE QLOCAL('MYQUEUE1') MAXDEPTH(1000) QDPMAXEV(DISABLED) QDEPTHHI(80)
    QDPHIEV(ENABLED) QDEPTHLO(20) QDPLOEV(DISABLED)

Figure 8. Queue depth events (1)

 

Commentary

Figure 8 shows how the queue depth changes over time:

1. At T(1), the queue depth is increasing (more MQPUT calls than MQGET calls) and crosses the Queue Depth Low limit. No event is generated at this time.

2. The queue depth continues to increase until T(2), when the depth high limit (80%) is reached and a Queue Depth High event is generated.

   This enables both Queue Full and Queue Depth Low events.

3. The (presumed) preventive actions instigated by the event prevent the queue from becoming full. By time T(3), the Queue Depth High limit has been reached again, this time from above. No event is generated at this time.

4. The queue depth continues to fall until T(4), when it reaches the depth low limit (20%) and a Queue Depth Low event is generated.

   This enables both Queue Full and Queue Depth High events.

Table 10 summarizes the queue event statistics and Table 11 summarizes which events are

Table 10. Event statistics summary for queue depth events (example 1)

	Event 2	Event 4
Time of event	T(2)	T(4)
Type of event	Queue Depth High	Queue Depth Low
TimeSinceReset	T(2) - T(0)	T(4) - T(2)
HighQDepth (Maximum queue depth since reset)	800	900
MsgEnqCount	1157	1220
MsgDeqCount	357	1820

Table 11. Summary showing which events are enabled

Time period	Queue Depth High event	Queue Depth Low event	Queue Full event
Before T(1)	ENABLED	-	-
T(1) to T(2)	ENABLED	-	-
T(2) to T(3)	-	ENABLED	ENABLED
T(3) to T(4)	-	ENABLED	ENABLED
After T(4)	ENABLED	-	ENABLED