We've got some discussion here about DSN ENQueueing and DEQueueing in batch jobs.
Is is my understanding and experience that the initiator will ENQ on all data sets referenced in the JCL (all steps) at job initiation time. The job will not start even the first step before all ENQs have been granted. So a job might be "WAITING FOR DATASETS" even if the one not yet available is only referenced in step nn (nn > 1). At step end, the initiator will DEQ any DSNs that are no longer needed, i.e. those which are not referenced on a DD in any later step. It is also my understanding that this is initiator business and therefore works the same way in either JES2 or JES3 environments. (I don't talk about main device secheduling in JES3, which only handles devices, not DSN ENQs). My colleague claimes that he once was told by an ISV that in a JES2 environment two jobs can be serialized on a certain step by coding a DISP=OLD/MOD DD for a data set in the step to be seriallzed. The jobs would then execute in parallel until they come to that specific step. They also said that this will not work in a JES3 environment because JES3 behaves as I described above. This contradicts my understanding (and experience). Can anybody enlighten me if this has changed in either JES2 or JES3, and if so when this change happended. I seem to remember as far back as MVS/XA that the job-level-ENQ behaviour is how it works. Am I wrong? Peter Hunkeler CREDIT SUISSE ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
