I didn't see where Lynn mentioned VSAM development, but several Future Systems posts leading to https://en.wikipedia.org/wiki/IBM_Future_Systems_project , where it became S38, AS/400, IBM i.
https://www.garlic.com/~lynn/index.html#archpost is his posts. On Fri, May 24, 2024 at 7:36 PM rpinion865 <0000042a019916dd-dmarc-requ...@listserv.ua.edu> wrote: > > What you described about VSAM is what I heard too, a replacement of the then > dominant access methods. > > Sent from Proton Mail Android > > > -------- Original Message -------- > On 5/24/24 8:18 PM, Joel C. Ewing <jce.ebe...@cox.net> wrote: > > > VSAM KSDS datasets were a clear win as a replacement for Indexed > > Sequental (ISAM) datasets when adding large numbers of keyed records. I > > saw cases where a KSDS implementation literally ran two orders of > > magnitude faster than ISAM and also took less DASD space, because ISAM > > required that unblocked overflow records be serially searched when > > there was no remaining space in a block to insert a record with a given > > key. > > > > In theory an ESDS dataset could be used to replace a sequential dataset > > and BSAM/QSAM, but of course the application interfaces were > > considerably different, and VSAM constraints on block size meant you > > could take substantial hits on track efficiency and performance for > > certain logical record sizes. > > > > An RRDS could be used as a functional replacement for direct access > > files, but again the restriction on block sizes caused compatibility > > issues, and tuning RRDS dataset access to get performance comparable to > > a well-tuned BDAM application was difficult to impossible. > > > > You could probably have designed a functional replacement for PDS > > datasets with either a KSDS or RRDS organization, or a combination of > > KSDS and ESDS, but it wouldn't have been practical. Many decades later > > PDSEs are almost a tranparent replacement for a PDS, but there are still > > some things possible with a PDS that are not supported for a PDSE. > > > > If VSAM's goal was to replace all other file organizations, it failed. > > The only old dataset organization to be made totally obsolete by VSAM > > was ISAM. > > > > JC Ewing > > > > On 5/24/24 10:02, Paul Gilmartin wrote: > > > On Thu, 23 May 2024 22:24:06 -0500, Mike Schwab wrote: > > >> 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. > > >> > > > "complete replacement" of what, specifically? I have heard the > > > assertion that VSAM was intended to replace all other access > > > methods: QSAM, BSAM, BPAM, ... > > > > > > ... > > > > -- > > Joel C. Ewing > > > > ---------------------------------------------------------------------- > > 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 -- 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
