On 17 Jun 2005 14:04:51 -0700, in bit.listserv.ibm-main you wrote: >> -----Original Message----- >> From: IBM Mainframe Discussion List >> [mailto:[EMAIL PROTECTED] On Behalf Of Ron and Jenny Hawkins >> Sent: Friday, June 17, 2005 3:53 PM >> To: [email protected] >> Subject: Re: Emulating SELTAPE=NEXT on z/OS. >> >> >> John, >> >> Isn't the recommended algorithm Random? The Next algorithm >> favours causes a >> trend to low order drives as I recall. >> >> Ron > >I am not sure. It is not documented to my knowledge. What is happening >is mainly political in nature. Some jobs are running longer than in the >past. The programmer is insisting that it is due to tape I/O contention >and that the allocation of tapes is favoring the low addressed drives. >I've just done a report from Mainview (CMF) and the tape I/O activity >appears to be fairly consistant across all addresses when looked at as a >summary over two weeks.
Get the SMF stats for the job both before the problem started happening and current. See what has changed. If nothing has changed other than elapsed time, then look for contention. I remember one case where an application supervisor wondered why the job was taking more time. The SMF stats showed that the major file had grown significantly. Further research showed that control records designed to move records to another system didn't cover all of the transaction codes. Performance problem then became a business problem because these were charge records that weren't being forwarded and applied to the customer. SMF is your friend. > >My bad attitude is just getting worse. ---------------------------------------------------------------------- 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
