On Sat, Apr 5, 2014 at 8:34 AM, Paul Gilmartin <[email protected]> wrote:
> On Fri, 4 Apr 2014 20:11:59 +0000, Chase, John wrote: > > > >Update from the vendor: The scheduler DOES NOT attempt to acquire > exclusive allocation of a JCL member; it only needs READ access to the JCL > library. So, the entire incident is now explained by the errant user > somehow obtaining an allocation of that library with DISP=OLD, which "locks > out" "everybody" from that library "for the duration". > > > Sometimes source of similar problems: the C RTL updating a PDS > member obtains ENQ EXC SYSDSN. C programs are pretty commonplace > now; someone ought to submit a Requirement that the C RTL should > use ISPF-style ENQs on PDS members, at least optionallly. > Definitely optionally. What to do if the ENQ fails becomes a question as well. Fail the fopen() with some sort of "in use" (EBUSY?) return? Do a wait? If wait, then how long? Unlimited (well, an S522 is likely in this case)? User specified? Hum, now we need to change the parameters to fopen() or come up with a new fopen() function. How does this affect portability? > > More wishful: JCL should support a new DISP keyword to select ISPF-style > ENQs on PDS members so any program could benefit from the facility > with no code changes needed. > My personal opinion is that the advantage of this is not worth the cost to implement. And there are more questions. Is this a SHARED or EXCLUSIVE enqueue? Oh, that would be the DISP-equivalent, I guess. Hum, when is the ENQ issued? At start of job, like for SYSDSN, or at start of STEP? If this is an exclusive ENQ, should there be two ENQs; one for the entire DSN & one for the DSN+MEMBER? The DSN-only is what ISPF uses before it does a SAVE. This is to serialize writing into a PDS (which is not needed for a PDSE) to avoid "member data interleaving". > > -- gil > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to [email protected] with the message: INFO IBM-MAIN > -- There is nothing more pleasant than traveling and meeting new people! Genghis Khan Maranatha! <>< John McKown ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
