On Tue, Apr 21, 2015 at 3:00 AM, Steff Gladstone <[email protected]> wrote:
> Thank you all for for help. The obvious question that remains is: how > does the operating systen itself maintain a continuous ENQ over several job > steps for a dataset allocated in the first step with disp=(mod,pass)? Is > there a special privileged ENQ operation that only the operating system has > access to? > > No, there is not a special ENQ. The initiator TCB, which exists for as long as the initiator is running, issues the ENQ. The initiator (in general terms) is what reads the parsed JCL and creates the SWA control blocks which represent the job. This code then knows the DSNs in the job and issues a single ENQ for _all_ of them before starting the first step. As each step ends, the initiator does a DEQ on the DSNs which are not going to be used in subsequent steps. At the end of the job, it DEQs whatever DSNs are left. This means that you _could_ use a directed ENQ to put the DSN on the ENQ chain for the initiator TCB, as you mentioned in a previous post. But since the initiator does not know anything about that, it will not know to do a DEQ to release it at end of job. This is why you would need a terminating step to do the DEQ. Thinking about it a bit more, given what Mr. Relson said about RTM, doing this _should_ work even if the initiator terminates abnormally since RTM should clean up the ENQs during EOM processing. -- If you sent twitter messages while exploring, are you on a textpedition? He's about as useful as a wax frying pan. 10 to the 12th power microphones = 1 Megaphone Maranatha! <>< John McKown ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
