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 EwingJoel, 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.
-- 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
