Decide where to collect the trace records

As Table 1 shows, depending on the component, the potential locations of the trace data are:

In address-space buffers, which are obtained in a dump
In data-space buffers, which are obtained in a dump
In a trace data set or sets, if supported by the component trace

Table 1. Location of trace buffers for components
Component	Address-Space Buffer	Data-Space Buffer	Trace Data Set
SYSAPPC	No	Yes	No
SYSAXR	Yes	Yes	Yes
SYSBCPII	No	Yes	No
SYSBHI	Yes	No	Yes
SYSCEA	Yes	Yes	Yes
SYSDLF	Yes	Yes	No
SYSDSOM	Yes	No	Yes
SYSGRS	Yes	No	Yes
SYSIEFAL	Yes	No	Yes
SYSIOS	Yes	Yes	Yes
SYSJES	Yes	No	Yes
SYSjes2	Yes	No	No
SYSLLA	Yes	No	No
SYSLOGR	Yes	Yes	Yes
SYSOMV	No	Yes	Yes
SYSOPS	Yes	No	Yes
SYSRRS	Yes	Yes	Yes
SYSRSM	Yes	Yes	Yes
SYSTTRC	No	Yes	No
SYSSPI	Yes	No	No
SYSVLF	Yes	Yes	No
SYSWLM	Yes	No	Yes
SYSXCF	Yes	No	Yes
SYSXES	No	Yes	Yes

If the trace records of the trace you want to run can be placed in more than one location, you need to select the location. For a component that supports trace data sets, you should choose trace data sets for the following reasons:

Because you expect a large number of trace records
To avoid interrupting processing with a dump of the trace data
To keep the buffer size from limiting the amount of trace data
To avoid increasing the buffer size

Depending on the component, you might also want to dump the address-space trace buffers and data-space trace buffers.

Note: You may need to consider the amount of auxiliary storage required to back data space buffers. In general, most components which use data space buffers establish a small default value less than 500 kilobytes of virtual storage. Some components allow you to specify values up to 2 gigabytes. The SYSIOS component trace uses a default of 512 megabytes for data space buffers. You should consider SYSIOS and other component data space buffers to ensure that the potential cumulative effect of all CTRACE data space buffers for your system can be accomodated by the local page data sets that you have allocated. For more information on auxiliary storage, refer to z/OS MVS Initialization and Tuning Guide.