It's really a pretty complex issue, and here is some (very expensive) modeling software that can help. But the cost of the software and the expertise to use it sometimes isn't cost effective.
Rather than a 'hard cap', try a 'soft cap' (sub capacity billing). Works great for us. We pay for less than 100 of our 158 MSU's and yet we can use all 158 during load spikes (like a batch window). First, work with your IBM business partner and get some prices for various MSU ranges. Then try setting the soft cap to one that gives you price relief but not user anger. HTH and good luck. -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Adams, Tracy Sent: Thursday, March 26, 2009 3:14 PM To: [email protected] Subject: Performance problems Okay, this is a continuation of a previous post... First of all we have an 88 mip cpu that is not constrained in any way. RMF cpu intervals are 20% during the day and during the 3 hours of batch 100% like a good MVS system can do. So with the rising cost of software, mainly CICS, we are looking to cut the mainframe's capacity in half. Now in the simplest math, batch should double in time and daily rmf stat intervals will increase but still not hit 100%, as long as no other constraints are revealed. Some basic tests have revealed results that I can't explain. Response time in our IDMS transactional system during the day (as record via PMDC writing smf records translated by MXG). A typical SAS model of performance for a given online transaction would be 95% < .5, 4% < 1, 1 % > 1. When I set a hard cap at 90% the model looks more like 70% < .5, 15% < 1, 10% < 2 and 5% > 2 of that 1% > 3. When I set the hard cap at 75% the model looks more like 50% < .5, 15 < 1, 20% < 2 and 7% > 2 and 3% > 3. And when I set the hard cap at 50% the model looks more like 40% < .5, 25 < 1, 25% < 2 and 10% > 2 and 3% > 3. And the users now users are really complaining now. RMF type 70 records (cpu) for all four scenerios (100%, 90%, 75% and 50%) show averages in the 20% utilized. RMF type 74 records (IO) show avg resp in single digits. UIC hasn't fallen below 255 in 10 years. Batch... completed in the same time frame set at 25% as it did at 100%. So if the hard cap sets the amount of Service units consumed not the actual speed of the processor, why is response time in the online going so far south when the CPU is still running unconstrained? Why did batch not slow down? ---------------------------------------------------------------------- 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 NOTICE: This electronic mail message and any files transmitted with it are intended exclusively for the individual or entity to which it is addressed. The message, together with any attachment, may contain confidential and/or privileged information. Any unauthorized review, use, printing, saving, copying, disclosure or distribution is strictly prohibited. If you have received this message in error, please immediately advise the sender by reply email and delete all copies. ---------------------------------------------------------------------- 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
