Job submission

This section helps you to understand the job submission process and identifies tuning activities.

Recognizing the indicators

These items can identify a bottleneck in job submission:

• STATMSG(CPLOCK) identifies a long HOLD time for the WSA.
• STATMSG(CPLOCK) identifies a long WAIT time for the EMGR, NMM, and GS when compared to the WSA.
• Long queue of operations in R status with no extended status and no reason documented on panel EQQSOPSP.

Breaking down the process

To submit a job, IBM Tivoli Workload Scheduler for z/OS must:

• Identify the best candidate. After the current plan lock is obtained, the ready operations are sorted according to their relative priority. The value of the QUEUELEN keyword of JTOPTS identifies the maximum number of ready operations that will be started by the WSA each time it enqueues on the current plan lock.
• Retrieve JCL:
  • Influenced by the number of PDSs and the number of members in the data sets concatenated on the EQQJBLIB ddname. If the PDSs are behind CACHE, the directory search is quicker.
  • Size of the EQQJBLIB members.
  • The performance of the user exits EQQUX001, EQQUX002, EQQUX009, and EQQUX013.
• Substitute and tailor JCL.
• Image the job input to the JCL repository (JS) file. The duration of this step is dependent on VSAM performance on the JCL repository.
• Submit to the internal reader. This function is performed by the submit subtask, which does not hold the current plan lock. So performance on the internal reader cannot effect other IBM Tivoli Workload Scheduler for z/OS subtasks. But it can ultimately affect the throughput of work on the processor.

Recommendations

Consider these recommendations:

• Use the EQQUX002 exit to locate the JCL in cases where there are many libraries concatenated on EQQJBLIB and the target library is predictable, perhaps according to the workstation name, or jobname, for example.
• Concatenate only libraries of interest to IBM Tivoli Workload Scheduler for z/OS on EQQJBLIB. Ensure the libraries are concatenated in frequency order. That is, if more than 50% of the JCL is stored in one library, that library should be the first concatenated on EQQJBLIB. If facilities are available, keep the directories for these libraries in storage.
• Defining FREESPACE on the JCL repository (EQQJS1DS and EQQJS2DS) is essential.
• Examine the performance of EQQUX001, EQQUX002, and EQQUX013, if used. The current plan lock is held while the three exits are called, performance is critical.
• Use VARSUB(SCAN) instead of VARSUB(YES) when JCL tailoring is required.
• If there are often many ready operations to be started, consider setting a higher QUEUELEN value. Once the WSA has the lock, submissions are handled very quickly. A well-tuned system can submit tens of operations per second.
• Examine JES performance, particularly on checkpoint data set, because this greatly affects the internal-reader submit time.