Speed? IIRC ISAM was awfully slow, especially if you didn't do mass updates in high-key to low-key order (I remember at one of my early employers we saved a TON of elapsed time in a nightly batch-add-update with that trick).
The VISAM that I am familiar with was a product of the ISV I worked for back then. Written in Pascal/VS and using a modified B*Tree indexing and block-linking methodology. Quick and more recoverable after unexpected abends compared to ISAM, as I remember it. Peter -----Original Message----- From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of Charles Mills Sent: Wednesday, April 1, 2020 5:27 PM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: PARM= vs PARMDD= and symbol substitution Huh. Well then, what WAS the purpose of VISAM? Not arguing with you. Just wondering now. I KNOW my client had a home-grown hybrid ISAM/BDAM access methond. Charles -----Original Message----- From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf Of Tom Marchant Sent: Wednesday, April 1, 2020 11:13 AM To: IBM-MAIN@LISTSERV.UA.EDU Subject: Re: PARM= vs PARMDD= and symbol substitution On Wed, 1 Apr 2020 09:01:12 -0700, Charles Mills wrote: >I wonder if the true statement is "ISAM did not support updating a record if >the length changed." No, that's not true either. This from the previously mentioned ISAM Logiic manual: <quote> The WRITE KN macro instruction is used with the READ KU macro instruction to update variable-length records when the record length can change. The WRITE KN macro instruction allows the user to insert new logical records into the data set or to replace a variable-length logical record with one having the same key and possibly a different record length. </quote> ---- This message and any attachments are intended only for the use of the addressee and may contain information that is privileged and confidential. If the reader of the message is not the intended recipient or an authorized representative of the intended recipient, you are hereby notified that any dissemination of this communication is strictly prohibited. If you have received this communication in error, please notify us immediately by e-mail and delete the message and any attachments from your system. ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
