z/OS Tracing

Please! Verify all details or suggestions with the appropriate vendor and / or vendor's manuals.

Analyzing Traces

z/OS V1R12.0 MVS Interactive Problem Control System (IPCS) User's Guide
SA22-7596-07
MVS™ has a number of tracing facilities. The system saves these traces in storage buffers and can, for traces from the generalized tracing facility (GTF) or component trace, write the trace records to data sets.
Using IPCS you can format the entries of any trace in a dump or trace data set. You can also do the following with GTF and component trace records:

Selectively format records without deleting the unformatted data from the buffer or dump
Find the system and time stamp for each record.
Mix formatted GTF and component trace records without combining the unformatted data.
Reduce the number of records in a trace data set
Extract trace buffers from dumps
Combine a GTF or component trace records into a single data set from multiple trace data sets.

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Type of traces

System trace

System trace provides an ongoing record of hardware events and software events occurring during system initialization and operation. The system activates system tracing at initialization, which runs continuously, unless your installation has changed the IBM-supplied system tracing. After system initialization, you can use the TRACE operator command on a console with master authority to customize system tracing.
System trace writes trace data in system trace tables in the trace address space. System trace maintains a trace table for each processor.
Because system trace usually runs all the time, it is very useful for problem determination. While system trace and the generalized trace facility (GTF) lists many of the same system events, system trace also lists events occurring during system initialization, before GTF tracing can be started. System trace also traces branches and cross-memory instructions, which GTF cannot do.

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Master trace

Master trace is a diagnostic aid that maintains a trace table of console messages in virtual storage. When master trace is active, the master trace table is embedded in dumps that have the TRT option or contain the master scheduler's private address space. Master trace can eliminate the need to submit a portion of the system log to IBM^® if there are problems in message processing. It also can ensure that the messages accompanying a dump are the ones that correspond to the problem. The TRACE command controls master trace. For a more detailed description of master trace, see z/OS MVS Diagnosis: Tools and Service Aids.

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Component trace

Component trace is a diagnostic aid that system programmers can use to trace the action of certain system components. Component trace enables the programmer to use the TRACE command to start and stop component trace. The components that use the component trace command must first invoke the define component trace service and define the name of the component requesting the service and the name of the start/stop routine that will get control when the TRACE operator command is issued.

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Transaction trace

Transaction trace provides a consolidated trace of key events for the execution path of application or transaction type work units running in a multi-system application environment. By tracing the path of a work unit running in a single system, or (more importantly) across systems in a sysplex environment, that is being processed by multi-system transaction servers, subsystem interfaces, and resource managers, transaction trace enables a system programmer to debug problems in those environments.
The essential task of transaction trace is to aggregate data showing the flow of work between components in the sysplex that combine to service a transaction. Transaction trace traces events such as component entry, exit, exceptions and major events such as COMMIT, and ROLLBACK. Do not use transaction trace as a component tracing facility.

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Generalized trace facility (GTF)

The generalized trace facility (GTF) is a service aid you can use to record and diagnose system and program problems. GTF is part of the MVS system product, and you must explicitly activate it by entering a START GTF command.
Use GTF to record a variety of system events and program events on all of the processors in your installation. If you use the IBM-supplied defaults, GTF lists many of the events that system trace lists, showing minimal data about them. However, because GTF uses more resources and processor time than system trace, IBM recommends that you use GTF when you experience a problem, selecting one or two events that you think might point to the source of your problem. This will give you detailed information that can help you diagnose the problem. You can trace combinations of events, specific incidences of one type of event, or user-defined program events that the GTRACE macro generates.

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