Hello all, Oops, hit the Send key too soon.
Opinions about FREESPACE for an HSM MCDS have been attributed to "Mainstar" several times in this thread, and a request for someone at Mainstar to weigh in with an opinion. I can't speak for Mainstar, as I left there last July (and haven't seen anyone from Mainstar posting on this listserv since then). I did the research on how best to manage the record insertion within the MCDS, and my recommendation was misquoted here on the Listserv -- I recommended FREESPACE(0 50), and not (50 50). This recommendation was based on mapping reports from the Mainstar program, VSAM Manager, which allows you to "see" exactly where record insertion activity is occurring. In many HSM MCDSs, insertion activity occurs evenly - but heavily -- across the entire KSDS file as migration processing occurs. Typically, the activity is heavy enough that you simply can't stop the splits, and my research found that if you specified FREESPACE(0 50) at reorg time, you effectively set up the file at reorg load time as if the CA splits have already occurred. In one example, an MCDS of 1,800 cylinders was reorged every Sunday night. Within the first two days of the week, it suffered about 1,600 splits, which blew the MCDS out to about 3,400 cylinders. The elapsed time to do the CA splits could take upwards of an hour of overhead time within HSM during its data set migration process. By setting up the data set during load time with 50% full CA's, you've accomplished the same thing as the CA splits, but without costing you anything in the way of overhead I/O. There's a paper on the Mainstar website that I wrote that goes into much more detail on this. It can be found at www.mainstar.com, click on Technical Articles under the Resources tab, then search on HSM and Storage Management, and the article is titled HSM Control Dataset Tuning. Ron Ferguson ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
