Performance tuning

Monitoring and tuning performance is not the responsibility of a security officer. However, the security officer should ensure that users are not altering the performance characteristics of the system to speed up their own jobs at the expense of others.

Several work management objects affect the performance of jobs in the system:
  • The class sets the run priority and time slice for a job.
  • The routing entry in the subsystem description determines the class and the storage pool the job uses.
  • The job description can determine the output queue, output priority, job queue, and job priority.

Knowledgeable users with appropriate authority can create their own environment on the system and give themselves better performance than other users. Control this by limiting the authority to create and change work management objects. Set the public authority to work management commands to *EXCLUDE and grant authority to a few trusted users.

Performance characteristics of the system can also be changed interactively. For example, the Work with System Status (WRKSYSSTS) display can be used to change the size of storage pools and the activity levels. Also, a user with *JOBCTL (job control) special authority can change the scheduling priority of any job on the system, subject to the priority limit (PTYLMT) in the user’s profile. Assign *JOBCTL special authority and PTYLMT in user profiles carefully.

To allow users to view performance information using the WRKSYSSTS command but not change it, do the following action: 
GRTOBJAUT OBJ(CHGSHRPOOL) OBJTYPE(*CMD) +
          USER(*PUBLIC)   AUT(*EXCLUDE)
Authorize users responsible for system tuning to change performance characteristics: 
GRTOBJAUT OBJ(CHGSHRPOOL) OBJTYPE(*CMD) +
          USER(USRTUNE)   AUT(*USE)