If you use a tape management system, you should not pre-catalog tapes for the spool offload facility. If you pre-catalog a tape with a data set name and a tape catalog that have no match in the z/OS® system catalog, JES2 ends the program abnormally with an 8FB reason code and issues message $HASP078.

If you use pre-cataloged data sets, JES2 ignores any parameters you might have specified on the OFFLOAD(n) initialization statement. If the UNIT= parameter is ignored, you could overwrite another data set of the same name. Make sure the spool offload data set defined on the OFFLOAD(n) DSN= statement matches the data set you have cataloged.

JES2 limits pre-cataloged data sets to a 20-volume multi-volume expansion. When preparing to offload jobs and SYSOUT, make sure the data being offloaded does not require more than this limit. If you exceed the number of volumes, JES2 responds with an allocation abend. For example, if you pre-allocate and pre-catalog the offload data set and you specify 6 volumes in the allocation, you can expand up to 20 volumes. JES2 would abnormally end after the twentieth volume.

JES2 dynamically allocates the offload data set when the operator specifies that transmitting or subsequent receiving is to begin. JES2 supports simultaneous transmitting to and receiving from different offload data sets.