Lizette, >From the Storage side I would disagree that imbed and replicate degrade >performance. Yes, REPLICATE wastes space, and neither actually improve >performance, but there is no degradation.
IMBED was meant to reduce seek, and REPLICATE to reduce Latency. Thus the statement " have been obsoleted by newer, cached DASD devices" explains why they are no longer required. Ron > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On > Behalf Of Lizette Koehler > Sent: Wednesday, January 16, 2008 7:41 AM > To: IBM-MAIN@BAMA.UA.EDU > Subject: [IBM-MAIN] Performance issues with VSAM IMBED > > I have been reading the z/OS V1.7 to V1.9 Migration guide and though it > states you do not need to remove IMBED, REPLCIATE or KEYRANGE. It does > mention that there is a performance issue by having them on your VSAM > files. > > I was wondering if anyone did an analysis to see what the buy back for > VSAM response was if these are removed? It would help me build a case > to get the VSAM data sets reorged more quickly. My VSAM seems to be > strictly IMBED at this time. I did not find any KEYRANGE or REPLICATE > definitions. > > Redefine existing VSAM data sets that contain the IMBED, REPLICATE, and > KEYRANGE attributes > > Description: No supported release of z/OS honors the IMBED, REPLICATE, > and KEYRANGE attributes for new VSAM data sets. In fact, using these > attributes can waste DASD space and often degrades performance. > Servicing these VSAM data sets has become increasingly difficult. In > some cases, unplanned outages have occurred. For these reasons, IBM > recommends that you stop using IMBED and REPLICATE, and that you > minimize or eliminate your use of KEYRANGE. IMBED and REPLICATE were > intended as performance improvements and have been obsoleted by newer, > cached DASD devices. Striped data sets provide much better performance > than KEYRANGE and should be viewed as a candidate for any existing > KEYRANGE data sets. > > > Is the migration action required? > No, but recommended to avoid degraded performance and wasted DASD > space. > > > Any comments are always welcomed. > > Lizette > > ---------------------------------------------------------------------- > 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 ---------------------------------------------------------------------- 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
