Fast Path external trace

Unexpected DL/I status codes or abends such as U1026 are examples of problems with Fast Path DL/I calls. Fast Path external trace is best suited for diagnosing problems that can be easily recreated, and is not intended to be run routinely because the overhead and output volume of the trace can be large. Fast Path external trace is intended for use primarily by IBM® Software Support, but users might also find it useful. IBM Software Support specialists might ask you to capture Fast Path external trace data for analysis by IBM specialists.

Fast Path external trace traces only dependent region activity; you cannot use it to collect data on control region processes. Because most Fast Path DL/I call flow is normally processed in the dependent region, this limitation is not serious. However, if you specify the PARDLI=1 option, DL/I processing is performed under the CTL TCB, which limits the usefulness of Fast Path external trace.

Recommendation: Do not trace PARDLI=1 execution. Create the problem again, if possible, without specifying the PARDLI=1 option.

The Fast Path trace entries are documented in Fast Path trace entries.