Ron, The correct parameters for System Managed Blocksize have been discussed before, and I think it is still a moot point. Using BLKSIZE=0 or omitting the BLKSIZE parameter will invoke SDB, but in both cases there must be enough additional information, such as LRECL and RECFM, to allow SDB to figure out the DSORG and optimal BLKSIZE.
VSAM also uses SDB-like allocation when CISZ is not specified, but if you have pumped up the CISZ in the same way as you have for DSORG=PS files there is not the same benefit because VSAM will optimise the underlying physical Blocksize. Compression across the board is not always a good thing as there is a CPU cost that can impact programs that are already CPU bound. Typically I find compression helps where a file is written once and then read many times because decompressing the files uses far less CPU then compressing it. Compressing files large files can also help when you run Synchronous Remote Copy and writing a large file is in your critical path. Ron > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On > Behalf Of David Speake > Sent: Tuesday, 14 February 2006 2:48 AM > To: [email protected] > Subject: Re: DASD allocation guidelines > > I think your best answer here may be the shortest one. > Use BLKSIZE=0 and overallocate a bit with RLSE and let > the system take care of it. Another thought is to use > extended format QSAM files with software compression > and striping via DFSMS. > > ---------------------------------------------------------------------- > 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
