TPs can use the same JES SYSOUT functions available to other MVS applications, with the exception that SYSOUT data sets allocated by TPs are treated as spin data sets. As with non-spin batch data sets, TP SYSOUT data sets are processed when they are unallocated. When FREE=CLOSE is coded in the SYSOUT specifications in the TP profile JCL, unallocation of the spin data set occurs immediately after it closes.

When a TP is scheduled as standard, its transaction initiator unallocates data set resources when the TP ends. When a TP is scheduled as multi-trans, it runs under a shell which, between requests, does not do the normal cleanup of a transaction initiator. Thus, the SYSOUT data set is not processed until all requests for the multi-trans have completed and the multi-trans ends. Multi-trans TPs that create output must close their SYSOUT data sets after each request completes. To guarantee processing of SYSOUT data, code FREE=CLOSE on TP profile SYSOUT specifications, or include the CLOSE macro with the FREE option within the TP.

To guarantee that SYSOUT data sets are processed before initiator cleanup, IBM® recommends that all SYSOUT specifications, for both standard and multi-trans TPs, include the FREE=CLOSE parameter.