Lizette, Without meaning to 'teach grannies to suck eggs', the index component of a VSAM KSDS contains an 'INDEX SET' and a 'SEQUENCE SET'. The 'INDEX SET' contains one or more CIs whose records/entries point at 'SEQUENCE SET' CIs. The records in the 'INDEX SET' are pointers to CAs, i.e. to 'SEQUENCE SET' CIs. The records in the 'SEQUENCE SET' CIs are pointers to DATA CIs. In both cases, these records contain the highest KSDS keys in the CA's CIs pointed at (for 'INDEX SET') or contain the highest KSDS CI key within a CA (for 'SEQUENCE SET') - thus allowing determination of the CI that contains the keyed DATA record, within the CA. Both 'INDEX SET' and 'SEQUENCE SET' CIs are subject to INDEX CI-splits when new 'user' keyed DATA records are inserted. The process of locating/accessing a VSAM KSDS DATA record is then as follows: - From the 'INDEX SET' determine which CA has the CI that contains the keyed DATA record. - From the 'SEQUENCE SET' determine which CI within that CA contains the keyed DATA record. - From this CI's CIDF and RDFs now locate/access the keyed DATA record. Performance will be degraded if the 'INDEX SET' has suffered CI-splits, because its lower level CIs will then have to be I/O fetched to read their pointers to the 'SEQUENCE SET' CIs. I would suggest that you dump your VSAM's INDEX dataset (e.g. "PRINT IDS(<whatever your VSAM index DSN is>) OUTFILE(<e.g. PRTFILE>)") to check for INDEX CI-splits - and down to what level - then figure out how to redefine your VSAM INDEX (CISZ, CYL/TRK etc.) from there. HTH. Cheers, Chris Poncelet (retired sysprog)
On 31/08/2020 13:48, Lizette Koehler wrote: > According to the LISTC it has CA-RECLAIM(YES) > > > > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of > Allan Staller > Sent: Monday, August 31, 2020 5:17 AM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Re: Simple VSAM question on sizing INDEX component > > Is the data set (and dfsms) set up for CA_RECLAIM? > > -----Original Message----- > From: IBM Mainframe Discussion List <IBM-MAIN@LISTSERV.UA.EDU> On Behalf Of > Lizette Koehler > Sent: Sunday, August 30, 2020 5:12 PM > To: IBM-MAIN@LISTSERV.UA.EDU > Subject: Simple VSAM question on sizing INDEX component > > [CAUTION: This Email is from outside the Organization. Unless you trust the > sender, Don’t click links or open attachments as it may be a Phishing email, > which can steal your Information and compromise your Computer.] > > List - > > > > I have a VSAM Dataset that has grown over the years. When it was set up - > the INDEX space was left to default > > > > I am wondering if it makes sense to override the Track Allocation and put it > in Cylinders. > > > > We are noticing a little bit of an increase in run time during reorg. I was > wondering if this might be due to the data set having 3.4GB now. This file > is EA/EF so it can grow > > > > Over 4500 Cylinders on the Data > > And the index is using tracks 2 pri and 11 sec - size is now 2.4 MB > > > > > > During reorg we offload records to an archive then reload the current data > back in. > > > > This may be something I cannot improve on, just thought I would see if there > are any insights I am missing. > > > > Process: > Offload the data to a temp file > > Archive records older than 2 weeks > > Del/Def VSAM dataset > > Reload current records to VSAM dataset > > > > This runs daily > > > Thank you > > > > Lizette > > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, send email to > lists...@listserv.ua.edu with the message: INFO IBM-MAIN > ::DISCLAIMER:: > ________________________________ > The contents of this e-mail and any attachment(s) are confidential and > intended for the named recipient(s) only. E-mail transmission is not > guaranteed to be secure or error-free as information could be intercepted, > corrupted, lost, destroyed, arrive late or incomplete, or may contain viruses > in transmission. The e mail and its contents (with or without referred > errors) shall therefore not attach any liability on the originator or HCL or > its affiliates. Views or opinions, if any, presented in this email are solely > those of the author and may not necessarily reflect the views or opinions of > HCL or its affiliates. Any form of reproduction, dissemination, copying, > disclosure, modification, distribution and / or publication of this message > without the prior written consent of authorized representative of HCL is > strictly prohibited. If you have received this email in error please delete > it and notify the sender immediately. Before opening any email and/or > attachments, please check them for viruses and other defects. > ________________________________ > > ---------------------------------------------------------------------- > 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 > . > ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
