Queue depth events: example 1

A basic sequence of queue depth events.

Figure 1 shows the variation of queue depth over time.

Figure 1. Queue depth events (1)
Illustration showing a graph of queue capacity against time. There are five points along the time axis: T0 is the initial point of interest. The queue capacity is at 0%. At T1 the queue capacity has increased to 20%. This is the depth low limit. At T2 the queue capacity has increased to 80%. This is the depth high limit, so a Queue Depth High event is generated. At T3, after peaking at around 90%, the queue capacity has decreased back to 80%. This is the depth high limit. At T2 the queue capacity decreases to 20%. This is the depth low limit, so a Queue Depth Low event is generated.

Commentary

  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.

Event statistics summary

Table 1 summarizes the queue event statistics and Table 2 summarizes which events are enabled.

Table 1. 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 2. 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