Can downgrade from Exclusive (NEW,MOD,OLD) to Shared (SHR) within a job. Cannot upgrade from Shared to Exclusive within a job.. Since the first job was SHR, another system / job / task may be browing the data, and prevents a Shared enque being upgraded to Exclusive enque. This is documented for within a job. I am guessing the Exclusive enque process requires no one be using the DSN at the time of the attempt, but that is not documented on https://www.ibm.com/docs/en/zos/3.1.0?topic=statement-disp-parameter
On Thu, Nov 30, 2023 at 9:24 AM Schmitt, Michael <[email protected]> wrote: > We had a production job enqueue failure on z/OS 2.4, that it seemed to me > should have worked. I've been in communication with IBM; they say it is as > expected. But I don't understand why this is normal. Does it make sense to > you? Has it always worked this way? > > Here's the scenario: > > We have a job where the first step has DD DSN=data.set.name(0),DISP=SHR. > The second step has the same data set, but as exclusive: DD DSN= > data.set.name(0),DISP=OLD. > > Someone was browsing the data set when the job started, so they were > holding a shared enqueue. > > The first step ran, and then the second step failed with the IEF211I - > DATA SET RESERVATION UNSUCCESSFUL error. > > > My understanding is that JES acquires the enqueues at the highest level > before starting the job, to prevent deadlocks. IBM says that because it is > a relative GDG, it is unable to acquire the enqueue on the *absolute* > generation before the job started. > > > Contrast it with this case: > 1st step: DD DSN=data.set.name(0),DISP=OLD > 2nd step: DD DSN=data.set.name(0),DISP=SHR > And again, a user is browsing the data set. > > In this case, the job waits until the user's enqueue is released. Which > means that JES tried to get the exclusive enqueue before starting the job, > so waits. Or it means that it stated the job, couldn't get the enqueue, but > waits instead of failing with the IEF211I error. > > So why is the second case different than the first? > > > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > -- Mike A Schwab, Springfield IL USA Where do Forest Rangers go to get away from it all? ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
