All speculation on my part. One system with no DASD, you need neither. On a system with only one, of just a few DASD volumes, a VTOC is required to say where on the volume a dataset is and the basic attributes of PS and PDS datasets.
Once you get to several always mounted DASSD volumes, it becomes a pain to need to remember and specify VOLSER in the JCL. CVOLs where an early attempt to solve this problem. Then came VSAM (and VVDS?) and VSAM Catalogs, and somewhile later ECf/Catalogs. Followed by SMS and VVDS for non-VSAM datasets > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On > Behalf Of Mike Schwab > Sent: Thursday, May 23, 2024 8:24 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: VTOCs vs. catalogs > > [EXTERNAL EMAIL] > > For the most part the catalog lets you locate your dataset no matter which > volume you put it on. > For non-vsam, that is about all that is stored, dataset characteristics are > in the > VTOC. > And with non-SMS volumes you can have uncataloged datasets on DASD or > tape. > > VSAM came from the Future Systems development as a complete > replacement, Lynn Wheeler has posts about that. > It was cut back to be an addition to MVS, then combined with CVOL catalogs > to ICF. > > On Thu, May 23, 2024 at 9:32 PM Phil Smith III <li...@akphs.com> wrote: > > > > I'm curious whether any of you old-timers can explain why we have both > > VTOCs and catalogs. I'm guessing it comes down to (a) VTOCs came first > > and catalogs were added to solve some problem (what?) and/or (b) catalogs > were added to save some I/O and/or memory, back when a bit of those > mattered. But I'd like to understand. Anyone? > > > > > > ---------------------------------------------------------------------- > > For IBM-MAIN subscribe / signoff / archive access instructions, send > > email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN > > > > -- > Mike A Schwab, Springfield IL USA > Where do Forest Rangers go to get away from it all? > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send email to > lists...@listserv.ua.edu with the message: INFO IBM-MAIN ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
