Using the problem determination aid facility

During DFSMShsm processing, the problem determination aid (PDA) facility gathers diagnostic information about DFSMShsm processing, stores this information in a circular file within storage, and periodically writes it to a circular file on DASD. This type of file appends data until full; then, starting at the beginning of the file, subsequent incoming data overwrites the data already there. For each DFSMShsm host, the circular DASD file consists of two data sets: ARCPDOX and ARCPDOY. ARCPDOX is the active data set. You can make ARCPDOY become the active data set and ARCPDOX become the inactive data set by issuing the SWAPLOG PDA command. This allows you to take the active data set and make it inactive for the purpose of examining the diagnostic information that has been gathered.

For detailed information on using the problem determination aid or calculating the PDA log data set sizes, refer to z/OS DFSMShsm Implementation and Customization Guide.

There are several reasons why you will at times want to collect and save PDA trace data. The following reasons are most common:

A trace showing DFSMShsm’s operating history can pinpoint the activity at the time the problem first occurs. This information can be helpful due to the time difference between when a problem first occurs and when it is first detected.
A trace can locate points of contention when two separate tasks conflict with one another.
A trace can help you to determine if a suspected DFSMShsm problem really exists, or if it is an operational error.
A trace may help locate a “missing” data set. You can scan for the last occurrence of the data set name.
Traces are needed to supplement dumps when you contact your IBM® support.

Two very useful functions can help you to extract the exact information you need from the PDA files. By using either or both the ISPF browse function and ARCPRPDO (PDA trace formatter) program, you may be able to solve your problem without assistance from IBM support.

The DFSMShsm trace formatter facility takes the raw trace data and organizes, reduces, and prints user-selected trace information. This is especially useful when you need specific data.

Use the trace formatter facility to:

Translate trace records into a readable format
Edit raw trace data
Select records based on your specific criteria

Conditional tracing is available to allow users to turn off some of the problem determination aid (PDA) tracing that is normally performed. Reducing the number of trace points can improve the performance of PDA tracing, as well as reducing the amount of data to analyze. However, when using conditional tracing, there is the possibility that the system may not capture needed data on the first failure. Users may have to turn off conditional tracing and recreate the problem.

The default for tracing is to trace everything. You may use conditional tracing to turn off some of the tracing functions. You use the PATCH command to turn off the functions. See z/OS DFSMShsm Implementation and Customization Guide, Chapter 16, "Tuning DFSMShsm," for examples of the PATCH commands that DFSMShsm uses to implement conditional tracing.