Frankly, the increase in run time is not what I would expect at all. But, to answer the OP's question, it is plausible given some specific situations.
That said, I agree with you that more questions need to be asked and you presented some very good places to look. -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Joel C. Ewing Sent: Thursday, February 09, 2012 2:49 PM To: [email protected] Subject: Re: Turning on additional CPs But would you really expect an effect of more than a few percentage points in the efficiency of one CP from only going from 3 to 4 engines? If you are seeing a large difference in run time, perhaps you should also look for an explanation that can produce a much larger difference than the MP effect. Maybe by removing a CPU bottleneck you have moved your major system constraint elsewhere, either to real memory or to DASD throughput, or some logical interlock. Perhaps the longer running jobs are now doing significant paging because of greater contention for real memory, or are having to wait on physical I/O to DASD more -- because other things that used to be too starved for CPU to compete are now running and using resources other than CPU that used to be more plentiful in a CPU-starved environment. JC Ewing On 02/09/2012 12:04 PM, Hal Merritt wrote: > I suppose that is reasonable for a single threaded, CPU bound job as a little > is lost from each engine as another is added. However, you should be able to > run more concurrent work giving a better over all through put. > > Another benefit of another engine is that, if not needed for anything else, > z/os likes to direct I/O interupts to just one engine. This allows the other > engines run a little smoother and again should increase your overall > thoughput. > > -----Original Message----- > From: IBM Mainframe Discussion List [mailto:[email protected]] On > Behalf Of gsg > Sent: Thursday, February 09, 2012 10:39 AM > To: [email protected] > Subject: Turning on additional CPs > > We have a z10 with 4 engines. Since upgrading to this box, we were only > running 3 engines. However, we recently turned on the 4th engine. We > noticed that several jobs started running longer, which we didn't expect. > Could turning on additional engines actually make a job run longer? > Also, where can I find any read material on the affect of turning on/off > engines. > > > TIA ... -- Joel C. Ewing, Bentonville, AR [email protected] ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN 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: INFO IBM-MAIN
