I expect it's because VIO requires cycles. Definitely true when simulating a device in memory. Quite possibly also true when doing VIO to page data sets on disk.
What I used to call the "DIM Coffee Table Book" :-) showed VIO to Expanded Storage burnt CPU compared to doing it to straight temp data sets on disk. For MOST data points. Martin Martin Packer Performance Consultant IBM United Kingdom Ltd +44-20-8832-5167 +44-7802-245-584 [EMAIL PROTECTED] From: "O'Brien, David W. (NIH/CIT) [C]" <[EMAIL PROTECTED]> To: [email protected] Date: 12/05/2008 17:51 Subject: Question concerning performance, VIO and chargeback We are running Z/os 1.7. It recently came to my attention that VIO had been implemented in such a way that temp datasets no matter how small ALWAYS went to DASD. One of my predessesors used a storclas with Guaranteed Space. Anyway a user asked to be able to use VIO so I turned it on. Today he comes back with test results showing higher chargeback for CPU when using VIO. My question is - How is this possible? We are processing the same numbers of records and eliminating some physical I/O and the CPU usage is higher. The total CPU for the job doubled. I would have thought that eliminating some of the channel activity would have reduced CPU usage. Can someone explain this to me? Regards, Dave O'Brien ---------------------------------------------------------------------- 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 Unless stated otherwise above: IBM United Kingdom Limited - Registered in England and Wales with number 741598. Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU ---------------------------------------------------------------------- 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
