John, As Yifat says, the CA split process may impact performance, but once the CA split is complete it does not affect performance at all.
A process that reorganizes a KSDS every time it has more than "n" number of CI or CA splits is not really improving any performance. In fact, it may be degrading performance as CI and splits once again go through a period of finding their natural level based on the key ranges with the highest insert activity. If CA, and perhaps CI splits are causing a performance problem, the usual strategies would be: 1) Use a larger CISZ. This makes the CA split faster and creates a larger buffer to absorb inserts after the CI split 2) Use FreeSpace to mitigate or eliminate CA and CI split activity CA splits may noticeably impact sequential scans of a KSDS if more than 10% of CAs have split, and become quite obvious if more than 30% have split because it would cause IO to behave in a skip sequential manner and defeat sequential pre-fetch in the controller. Ron > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of > John McKown > Sent: Thursday, October 21, 2010 4:15 PM > To: IBM-MAIN@bama.ua.edu > Subject: Re: [IBM-MAIN] DFDSS VSAM logical restore? > > On Thu, 2010-10-21 at 13:55 +0200, Yifat Oren wrote: > > John, > > > > I would have used SORT-COPY (but if it's DFSORT make sure the VSAM BUFND > > setting is optimal). It should be faster than IDCAMS (because of the better > > TAPE I/O). > > > > Are you sure you need to reorg at all? > > > > I'm sure you are familiar with the "cost of CA splits is mainly at split > > time", etc., and re-org potentially causing more CA splits if it reverses > > needed splits .. > > > > How did CA-FAVER solve this problem? In-place reorg? > > > > Best Regards, > > Yifat > > > > We would FAVER EXPORT the DSN to tape, then FAVER IMPORT it back. The > actual job is more complicated than that. We use "wild cards" to dump > multiple VSAM files to tape for backup purposes. We then run T-REX to > list all of those with a large number of CA splits. We message that > report in the next step to create FAVER control cards to IMPORT selected > VSAM files. FAVER IMPORT, like IDCAMS IMPORT will delete and redefine > the entire VSAM SPHERE based on the cluster names given. > > The cost to convert from FAVER in terms of labour will be immense. So I > hope CA comes through for us. My boss has been trying hard to drive our > costs down because that helps save jobs. > > -- > John McKown > Maranatha! <>< > > ---------------------------------------------------------------------- > For IBM-MAIN subscribe / signoff / archive access instructions, > send email to lists...@bama.ua.edu 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 lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
