From memory: No z/OS dataset can span more than 59 volumes. 16 extents can reside on each volume unless the data set is SMS-managed and the DSNTYPE is defined as 'EXTENDED', in which case up to 123 extents can reside on each volume. However, unless Extent Constraint Removal is specified as 'Y' in the DATACLAS, the total number of extents spanning all volumes is 255.
-----Original Message----- From: IBM Mainframe Discussion List <[email protected]> On Behalf Of Jon Perryman Sent: Friday, December 19, 2025 5:46 PM To: [email protected] Subject: Re: Multi volume dataset copy CAUTION: This email originated from outside of the Texas Comptroller's email system. DO NOT click links or open attachments unless you expect them from the sender and know the content is safe. On Fri, 19 Dec 2025 15:14:13 -0600, Mike Schwab <[email protected]> wrote: > PS has a 15 or 16 extent limit across all volumes. It's per volume (not all volumes). As for max volumes, isn't it 255? > Might already be compressed, and vsam overhead might not compress as well. Since the OP opted to use ADRDSSU backup & restore, the backup dataset can be deleted once the file is restored. Will compression be an issue since it's short term storage. If I'm correct about 255 volumes, then he can spread the backup across more than 15 volumes. The op should also note that primary and secondary sizes are not necessarily contiguous sizes. E.g. SECONDARY = 10 cyl doesn't require 10 contiguous cylinders as long 10 cylinders is available on the volume. The system will happily allocate 2 extents of 5 cyl. If I remember correctly, I think the OP can specify VOL=SER=(vol1,vol2,vol3,...) if the OP needs to manually search for space. If he's not using a shared catalog, then he'll probably need to specify volumes for the restore job. As for the restore job, this is a vsam dataset with freespace. Does anyone remember if ADRDSSU automatically reorganizes freespace? If so, the op will need to use the restore parm to use original dataset freespace to avoid using more than 15 volumes. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
