Norman, I must admit, this is the first time I have ever heard of the processors slowing down when they get hot. Do you have any doc to back this up?
Tom Harper IMS Utilities Development Team Neon Enterprise Software Sugar Land, TX -----Original Message----- From: IBM Mainframe Discussion List [mailto:[EMAIL PROTECTED] On Behalf Of Norman Hollander on h-WiZ.biz Sent: Tuesday, February 05, 2008 12:53 PM To: [email protected] Subject: Re: CPU time differences for the same job There have been several discussion at SHARE (in the EXCP project) over the past couple of years on just this topic. The variability of CPU time has been seen up to 20-30% different from run to run. The hardware itself may be part of the issue. The processors (from z990s to z9s) may slow down when they get too hot, and depending on which instructions are being executed and if the data has been fetched at the same time, the cycle time for the instructions can be very different. You could have a good conversation with Bob Rogers about this when next you see him. EWCP was concerned from a Capacity Planning and Chargeback position. It has been recommended that "banding" be used in Chargeback systems to account for the variability. It was also suggested that this variability will get worse before it gets better. So business as usual needs to be changed to cover this issue for Chargeback. And Capacity planning has just become more complicated. ---------------------------------------------------------------------- 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
