Understanding the ESP APPLFILE and TRAKFILE
Article ID: 385678
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Issue/Introduction
- What are the contents of the APPLFILE and TRAKFILE datasets and how their operational mechanisms work.
- Does an active APPL running on the Workload Director hold slots with respect to job count of the APPL ? For example, does an APPL with 150 job steps hold 150 slots while executing? If yes, does the APPL release those slots progressively while the steps are being completed or does it hold all the slots until the whole APPL is completed?
- What are the slot holding mechanisms behind APPLs that are in TROUBLE, APPLWAIT and WAITING statuses ? Does an APPL release the held slots automatically when the APPL is completed?
- What is the difference and relation between the number of slots and slot size?
- Is it possible to increase the number of slots and slot sizes. If yes, what are the effects of increasing the number of slots and slot size in terms of mainframe performance ?
- Is there an automated method to automatically completing the APPLs that are in TROUBLE or APPLWAIT statuses for a certain period of time ?
- Does the APPL that has not yet started but is queued in Workload Director until its scheduled times also hold slots during that period?
8. What is the relation between the number of slots, slot size and CPU Usage?
Resolution
Here are the basic information about the APPLFILE and TRAKFILE:
- They are slot files:
. Formatted and Managed by ESP;
. APPLFILE needs to be allocated as CONTINUOUS, and its size can be up to one volume;
. Wrap-around effect as slots are re-used: when the application or job completes, the related slots will be added to the chain for reuse. Note: if no more reusable slots, then the oldest application or job related slots will be used.
- Records all active applications or jobs;
- Has pointer (or index records) in JOBINDEX file, based on the INDEX value on the APPL statement or default 20 for applications, or INDEX on tracking module for JOBs. ESP will find the index records in JOBINDEX file and then locate the slots in the APPLFILE or TRAKFILE.
Note: The INDEX records will wrap-around the previously completed ones, and will keep up to 255 (limited by VSAM KSDS record length) for incomplete ones. For example, if the 21st application generation is created, and the previous 20 gens are not complete, then there will be 21 index records for this application; but if 19 gens are not complete, then the completed gen INDEX record will be dropped, so there will be 19+1=20 incomplete Index records.
Here are the answers to the above questions:
1. Refer to the above basic information about the APPLFILE and TRAKFILE.
2. No. One 4K slot in APPLFILE normally can hold 150 JOBs (this varies based on the type of JOBs), and the slot will be released after the whole APPL generation is completed. See more on the doc link below:
APPLFILE
3. The slots used by the incomplete application generations won't be marked as reusable, therefore they will be kept until there is no more reusable slot, when the slots for oldest application generation will be used for the new application generation.
4. Normally one default size slot should be enough to hold one small or medium application or job. More slots may be used for larger applications. If the slot size is increased (i.e., 16K) then even the small applications that require 1K space will now use 16K as one slot cannot split. As the result, the APPLFILE may need to be increased. We recommend to keep the applications in reasonable size.
5. Yes, programs CYBESUT3 for APPLFILE and CYBESUT4 for TRAKFILE can be used to increase the number of slots (through increasing the file size) and slot sizes. This should not cause any performance problem but may waste space in the files (see #4).
6. ESP provides the ISPF menu CSF extension CAA to complete applications. You may set up your own event/application.
7. If only the application generation is created, it will occupy the slot(s).
8. The slot and slot size won't affect the ESP CPU usage.
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