Generalized trace facility (GTF)

GTF is part of the MVS system that you can use to record CICS® trace entries.

You can use GTF to record CICS trace entries and use the interactive problem control system (IPCS) to produce reports. More generally, GTF is an integral part of the MVS system, and traces the following system events: DASD seek addresses on start I/O instructions, system resources manager (SRM) activity, page faults, I/O activity, and supervisor services. Execution options specify the system events to be traced.

GTF is generally used to monitor short periods of system activity and you should run it accordingly.

The amount of processing time that GTF uses can vary considerably, depending on the number of events to be traced. You should request the time-stamping of GTF records with the TIME=YES operand on the EXEC statement for all GTF tracing.

Run GTF at a dispatching priority (DPRTY) of 255 so that records are not lost. If the DPRTY is specified at 255 and GTF records are lost, specify the BUF operand on the execute statement as greater than 10 buffers.

You can use the following options to get the data that is generally needed for CICS performance studies:

TRACE=SYS,RNIO,USR     (VTAM)
TRACE=SYS              (Non-VTAM)

Note: VTAM® is now known as z/OS® Communications Server.

If you need data on the units of work dispatched by the system and on the length of time it takes to execute events such as SVCs and LOADs, the options are as follows:

TRACE=SYS,SRM,DSP,TRC,PCI,USR,RNIO

The TRC option produces the GTF trace records that indicate GTF interrupts of other tasks that it is tracing. This set of options uses a higher percentage of processor resources, so use it only when you need a detailed analysis or timing of events.

No data-reduction programs are provided with GTF. To extract and summarize the data into a meaningful and manageable form, you can either write a data-reduction program or use one of the program offerings that are available.

For further details, see z/OS MVS Diagnosis Tools and Service Aids.