Preventing Abnormal Termination of JES3 or a C/I FSS Address Space

To prevent abnormal termination of the JES3 global address space or a C/I FSS address space when there is not enough SWA space to store the scheduler control blocks derived from a job's JCL, specify an address space JCL statement limit. The address space JCL statement limit defines the maximum number of JCL statements that all CI DSPs in an address space can process concurrently.

For the JES3 global address space, specify the address space JCL statement limit using the MAXASST parameter on the STANDARDS initialization statement or the MAXASST= operand on the *F,X,D=CI operator command. For a C/I FSS address space, specify the address space JCL statement limit using the MAXASST parameter on the FSSDEF initialization statement or using the MAST= operand on the *F,F operator command.

Note: The address space JCL statement limit and the job JCL statement limit do not affect demand select (started task and TSO LOGON) jobs. This means that:

A demand select job can contain more JCL statements than either JCL statement limit allows.
When counting the total number of JCL statements that all CI DSPs are processing, JES3 does not count the JCL statements for demand select jobs.

However, demand select jobs generally use few JCL statements. Most installations will not encounter virtual storage constraint while converting or interpreting demand select jobs.

After you set the address space JCL statement limit(s), JES3 allows a CI DSP to process a job only if both of the following are true:

The number of JCL statements for the job is less than the address space JCL statement limit
The sum of the number of JCL statements for the job plus the number of JCL statements all CI DSPs are processing at that time in the address space is less than the address space JCL statement limit

If the first condition is not true, JES3 cancels the job. If the second condition is not true, JES3 makes the job wait. In addition, all jobs that have not yet begun MVS™ converter processing wait, while jobs that are into or past MVS interpretation continue processing.

After JES3 writes a job's JCL (as scheduler control blocks) to the spool, JES3 frees the SWA space. The total number of JCL statements that all CI DSPs are processing in the address space decreases by the number of JCL statements in the job. When this total decreases to a point where the waiting jobs can be processed without exceeding the address space JCL statement limit, JES3 allows the jobs to continue processing.