Or use IEBDG... > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf Of Joel C. Ewing > Sent: Thursday, June 21, 2012 6:00 PM > To: [email protected] > Subject: Re: [IBM-MAIN] SMS processing setup for secondary extents > > On 06/21/2012 07:47 PM, Joel C. Ewing wrote: > > On 06/21/2012 06:42 PM, Lizette Koehler wrote: > >>> From: "Joel C. Ewing" <[email protected]> > >>> > >>> And better yet, also use a DATACLAS with the Extended attribute so > >>> you are not constrained to only 16 extents per volume. > >>> > >>> With Space Constraint Relief. Extended attribute, and Dynamic Volume > >>> Count, both primary and secondary allocations will use as many > >>> extents and volumes as necessary to get the requested primary or > >>> secondary space (not just the 5 extents for primary, 1 for secondary > >>> limits of ordinary sequential dataset allocation), so fragmentation > >>> of free space is less of an issue. Since you are not guaranteed any > >>> minimal amount of space for any individual extent, you also need the > >>> larger extent count limit given by the Extended data set attribute > >>> to insure that you are not artificially restricted by number of > >>> extents from allocating available free space on the assigned volumes. > >>> > >>> Using these attributes you can even request a primary allocation > >>> that spans multiple volumes and guarantee that step execution will > >>> not even start if a large minimal primary space is unavailable, but > >>> you have to be careful using this because at least in the past the > >>> RELEASE option would not release allocated but unused space on > >>> volumes that contained no written data, only on the last used volume > >>> of the data set (so a multi-volume primary allocation used for a > >>> very small dataset could consume a large amount of pool space on > >>> subsequent unused volumes even after RELEASE). > >>> Joel C Ewing > >> > >> > >> Joel, I am not sure that would apply to a PDS. I know that for > >> nonvsam sequential files that will work, but I am not sure if it is a > >> PDS if it can go beyound 16 extents. I have been looking through the > >> manauls and cannot find a reference (info center - yuck). > >> > >> Can you comment? > >> > >> Lizette > > > > No, I'm pretty sure my remarks only apply to Extended Sequential > > datasets and that there is no "Extended" support for PDS or PDS/E data > > sets. VSAM datasets can also be Extended, but they have their own > > allocation rules. > > > > I interpreted the context of the original question to be about > > sequential datasets since multiple GDG datasets were being merged -- > > and the ability to create and work with GDG datasets that happen to be > > a PDS is not really documented and not generally known outside those > > of us that needed the capability, tried it, and found it worked > > (obviously you can't specify both a member name and a relative GDG > > number in JCL because of syntax restrictions). I gathered from > > discussion at one of the SHARE Q&A's over a decade ago that PDS/E's > > can't be a GDS because the PDS/E designers didn't appear to be aware > > that was one of the "features" of a PDS and the PDS/E implementation > > explicitly disallowed such usage. > > And I forgot to mention earlier that a simple way to test whether your > sequential datasets are being allocated as expected is to set up a job to > IDCAMS REPRO a moderately sized sequential dataset concatenated to > enough copies of itself to build up a sequential dataset equivalent to about > half a drive in the pool, and then use that concatenated to itself enough > times as input to another REPRO to convince yourself that extents for a > multi-volume output dataset are being allocated as expected and multiple > volumes are being used -- being careful to delete all your "junk" datasets > after inspecting the results. There is an IBM utility designed explicitly to > create a specified number of test records for a sequential dataset, but my > recollection is that it is incredibly slow and a CPU hog - much faster to use > IDCAMS REPRO. > > -- > Joel C. Ewing, Bentonville, AR [email protected] > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send email to > [email protected] with the message: INFO IBM-MAIN
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