A summary of performance bottlenecks, symptoms, and causes

This summary includes the symptoms you get if the performance of your system is restricted, and the specific causes of the delays at each point.

Table 1. A summary of performance bottlenecks, symptoms and causes
Bottleneck Symptoms Possible causes
Initial attach to transaction manager CEMT INQ TASK does not know task.

Tracing shows long wait for attach to transaction manager.
  • Interval on EXEC CICS START too long
  • Terminal not available
  • Remote system not available
Initial attach to dispatcher CEMT INQ TASK shows wait on MXT or transaction class.

Tracing shows long wait for attach to dispatcher.

 MXT or transaction class limits set too low
First dispatch Performance class monitoring shows long wait for first dispatch.

Storage statistics show CICS has gone short-on-storage (SOS).
  • MXT or transaction class limits set too low
  • Priority of task set too low
  • Insufficient storage
  • System under stress, or near it
SUSPEND / RESUME cycle Tasks take a long time to complete.
  • System loading high
  • Task timeout interval too large
  • CICS data sets are on volumes susceptible to MVS RESERVE locking