To avoid losing trace data because APPC/MVS has to suspend tracing activity, you may try any combination of the following tactics:

• Allow APPC/MVS to determine the optimal block size for the device on which the data set is allocated. To do so, allocate the data set without specifying the BLKSIZE operand.
• Make sure the API trace data sets reside on volumes that are not used heavily by other subsystems or applications. Separating trace data sets from other types of data sets might help reduce contention or delays because of frequent use and serialization.
• Filter ATBTRACE START requests as much as possible. For example, instead of collecting trace data for all instances of a TP, restrict tracing activity to only the conversations allocated for that TP with particular user IDs. Doing so can reduce the amount of trace data that is generated for an LU/TP combination.