Avoiding Loss of Data through Wrapping

To avoid losing trace data through wrapping, you need to make sure the primary space allocated for the data set is sufficient to contain all the trace entries. Determining the amount of primary space required might be a trial-and-error process, depending on how accurately you can estimate:

The number of LU/TP (and possibly user ID) combinations that will be traced into a particular data set. APPC/MVS does not limit the number of unique LU/TP combinations specified for tracing into a particular data set, but the more you specify, the greater the chance that wrapping will occur.
The number of calls your TP issues for APPC/MVS or CPI-C services. The more calls your TP issues (especially asynchronous calls), the more trace data will be generated.
How many instances of the TP run. If you have a TP that might run many times while tracing is on, the cumulative effect of its calls might easily fill the data set.

You might have to run a TP and review the collected trace data several times, and adjust the primary space accordingly, before determining an adequate amount of primary space. (See Reading Trace Entries When Wrapping Occurred if you need to determine whether wrapping has occurred.)

An alternative, which might be easier than determining the primary space for DASD, is to use a tape data set for the trace data. With tape, APPC/MVS can write trace entries into a total of five volumes. If you need more space, you can allocate the tape with a volume count, which increases the total to 255 volumes. The disadvantage to this approach is reduced usability: the trace data on tape has to be moved or copied over to DASD before you can view it.