Yes. Especially if the jobs are CPU bound. Going back to the discussion of dedicated vs. shared CPs. Etc.
There is a well know impact of additional CP's known as the "MP effect". Going from 1 to 2 engines does not get you twice as much horsepower. Only 1.9 times as much. In the early days 360/65 AP & 305/65 MP, the effect was only 1.7 times. Each additional processor increases the accumulated overhead of trying to keep everything in sync between the members of the group. 3 processors would (for example) (1+(1*.9)+(1*.8)) *.9) =2.7, not 3.0. This overhead is a non-linear relationship. The more processors, the greater (relatively speaking) the MP effect. i.e. less horsepower added per additional engine This is the reason IBM invented Hiperdispatch. By treating the processors as members of group (books), the MP effect is reduced and overhead is reduced.. CMG (www.cmg.org), Cheryl Watson (www.watsonwalker.com), Share (www.share.org) and IBM Techdocs (http://www-03.ibm.com/support/techdocs/atsmastr.nsf/Web/Technotes) are all good sources for additional information. HTH, <snip> 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. </snip> ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
