On Mon, 5 Mar 2007 11:27:20 -0500, John Eells <[EMAIL PROTECTED]> wrote:
>Mark Zelden wrote: >> >> >> Because some people actually care about speed of execution and CPU time. >> >> Example for just 1 library: >> >> COPY of SYS1.LINKLIB to new library (same blksize): >> >> CPU 0MIN 01.00SEC SRB 0MIN 00.93SEC (35 sec wall clock) >> >> COPYMOD of SYS1.LINKLIB to new library (same blksize): >> >> CPU 0MIN 03.36SEC SRB 0MIN 00.94SEC (2 min 28 sec wall clock) >> ><snip> > >I had not considered that. It would be interesting to know, if >one could, how much overhead would be saved *after* a COPYMOD, >though. The COPYMOD itself might be expensive, but the potential >downstream reduction in CCW chaining (which also has a CPU cost) >and fetch time (which has a CPU cost when Program Fetch's PCIs >aren't timely and a CCW chain must be rebuilt) might prove worth it. > >Without knowing the benefit, it's hard to say whether the cost is >justified. > I'm not saying COPYMOD shouldn't be used to reblock. But there is no reason (other than creating one size fits all JCL) to do it every time. Even if the loadmod was already reblocked from a previous run, COPYMOD does it again. Note that the test I ran above was using COPYMOD for a library of the same BLKSIZE that had already been loaded / copied with COPYMOD prior to the test (when ServerPac loaded SYS1.LINKLIB via COPYMOD). So all I'm saying is for your own JCL (occasional copies), go ahead and always use COPYMOD if you like waiting longer. But I would never suggest it be done for production jobs. Mark -- Mark Zelden Sr. Software and Systems Architect - z/OS Team Lead Zurich North America / Farmers Insurance Group: G-ITO mailto:[EMAIL PROTECTED] z/OS and OS390 expert at http://searchDataCenter.com/ateExperts/ Systems Programming expert at http://expertanswercenter.techtarget.com/ Mark's MVS Utilities: http://home.flash.net/~mzelden/mvsutil.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
