Choose an Appropriate Sleeping Interval

The Control‑M monitor "wakes up" according to the sleeping interval specified using parameter INTERVLM in member CTMPARM.

As the value specified for the sleeping interval increases, Control‑M uses less CPU and I/O for the following reasons:

• The job selection routine is invoked after longer intervals.
• The Control‑M monitor checks the status of submitted jobs after longer intervals.
• The Control‑M monitor interrogates the Active Jobs file (AJF) after longer intervals for additions or changes that may have been performed from batch or from the IOA Online facility.

However, if the value specified for the sleeping interval is too high, the following can result:

• Jobs may be scheduled with a delay.
• Processing a command entered using the IOA Online facility (for example, to hold a job) may take more time because the Control‑M monitor performs the command.

Do not overrate the importance of a job-scheduling delay. In many cases, increasing parameter INTERVLM from three seconds to six seconds can actually provide the same throughput, because many jobs that were submitted by Control‑M must wait for an initiator to become available.

The sleeping interval is not a fixed installation parameter. It can be changed dynamically during standard production hours (for example, according to hours, shifts, and so on), by scheduling a CTMOPR started task at the appropriate time. The started task issues the command

where

• ss is the interval in seconds
• th is the interval in hundredths of seconds

Another aspect to consider when deciding on the value of parameter INTERVLM is avoiding situations where the Control‑M monitor is faster than the local JES. This can be recognized when one of the following events occurs:

• Many CTM262S/JES262S messages are issued by the Control‑M monitor for different jobs. This happens when the job’s SYSOUT is already on the JES output queue, but JES does not allow access to it.
• The Control‑M monitor successfully submits a job to MVS, but the job does not appear in any JES queue for a long time, causing the job to receive a status of "disappeared". This situation is rare and only happens if JES is heavily overloaded.

This does not refer to a situation where JES is "stuck." Control‑M does recognize such a situation, and therefore does not submit the job.

If this happens at your site, consider increasing the value of parameter INTERVLM.