Changing job attributes for prestart jobs

Large job message queues can consume storage, can lead to large job logs which also consume storage, and can cause IPL performance problems when job message queues need recovery or cleanup during an IPL. This example shows how to change the job message queue full action (JOBMSGQFL) and job message queue maximum size (JOBMSGQMX) values for prestart jobs.

Note: The QDFTSVR job description was introduced in release V5R3M0 to do some of this for you.

To limit the size of job message queues for prestart jobs without affecting other jobs, follow these steps:

Find the prestart jobs that you want to affect and determine which job description is used by the prestart job entry. (To do this, use the Display Subsystem Description (DSPSBSD) command.)
Determine whether the job description is used by just the one prestart job entry (in which case you can just modify that job description) or used by multiple references such as user profiles, prestart job entries, other SBSD entries, and so on. (You can always create another job description for the "don't know" but if you know that a change to the existing job description affects only the jobs you want affected then you should just modify that particular job description.)
Create a new job description to be used by the prestart job entries that you want to affect. You can use the Create Job Description (CRTJOBD) command, but in this example we make a copy of the job description that is currently being used.
Note: If you have the job description JOBD(*USRPRF) you can use the Display User Profile (DSPUSRPRF) command to determine which job description is currently being used. The default configurations use job description QDFTJOBD or QDFTSVR.
DSPUSRPRF USRPRF(QUSER)
To avoid confusion with IBM-supplied objects, avoid names starting with the letter 'Q'. This example uses the name PJJOBD as the name of the job description for the prestart job entries. Use the Create Duplicate Object (CRTDUPOBJ) command to make a copy of the job description currently used by the QUSER user profile.
```
CRTDUPOBJ OBJ(QDFTSVR) FROMLIB(QGPL) OBJTYPE(*JOBD)
              TOLIB(QGPL) NEWOBJ(PJJOBD)
```
Match the object ownership and authorities of the job description that you copied. Since QDFTSVR and QDFTJOBD are owned by QPGMR, the example (below) shows how to change the newly created job description to be owned by QPGMR. Use the Change Object Owner (CHGOBJOWN) command and the Grant Object Authority (GRTOBJAUT) command to get the object ownership and public authority set correctly. You can find the owner and authorities by using the Display Object Authority (DSPOBJAUT) command.
```
CHGOBJOWN OBJ(QGPL/PJJOBD) OBJTYPE(*JOBD) NEWOWN(QPGMR) 

GRTOBJAUT OBJ(QGPL/PJJOBD) OBJTYPE(*JOBD) USER(*PUBLIC) AUT(*USE)
```
Use the Change Job Description (CHGJOBD) command to customize the job attributes. In this example, we use a value of 8 megabytes for the job message queue maximum size. Other values would also work as long as the limit is far less than 64 megabytes.
```
CHGJOBD JOBD(QGPL/PJJOBD) JOBMSGQMX(8) JOBMSGQFL(*WRAP)
            TEXT('Job attributes for prestart job entries')
```
Look through all of the prestart job entries that are active on your system. Use the Work with Subsystems (WRKSBS) command to get a list of all active subsystems. Use option 5 to display the subsystem description. Use option 10 to display prestart job entries and use option 5 to display details for the prestart job entry.
If the prestart job entry specifies USER(QUSER) and JOBD(*USRPRF), use the Change Prestart Job Entry (CHGPJE) command to specify the new job description.
```
CHGPJE SBSD(SBSLIB/SUBSYSTEM) PGM(PJPGMLIB/PJPROGRAM)
           JOBD(QGPL/PJJOBD)
```
If the prestart job entry specifies a job description, use the Change Job Description (CHGJOBD) command to change the JOBMSGQMX and JOBMSGQFL values in that job description.
```
CHGJOBD JOBD(JOBDLIB/JOBDNAME) JOBMSGQMX(8) JOBMSGQFL(*WRAP)
```

Details

The QDFTJOBD job description is used by many prestart job entries and is used many other places in the system. This example creates a single new job description named PJJOBD. The new job description is used by many prestart job entries but it is not used elsewhere. To use different values for different prestart job entries, use a different job description for each entry. Some prestart job entries already have unique job descriptions.

Some job attributes for prestart jobs cannot be changed using this procedure because they do not come from the job description that is used when starting the job. Many servers that use prestart jobs swap user profiles and then use the Change Job (QWTCHGJB) API to change a subset of the job attributes. The changed job attributes come from the job description used by the user profile to which the prestart job has swapped. Refer to the JOBC0300 format of the Change Job API for more information.

For some job attributes, the job description may indicate that the value is to be taken from a system value. When you change the system value, the change affects all jobs that get their job attribute from the system value. Changing the value in the job description affects only those jobs that get their job attributes from that job description.