> We are in the evaluation process for one or two > mainframe upgrades. Our current environment includes a z9EC 2094-504 with > 4 prod LPARs and 1 tech support LPAR with a total of 12 LP's, so a ratio of > 3:1. Some of the candidate mainframes have faster speeds but only 2 or 3 > CP's. This would give a ratio of 6:1 or 4:1, and even higher (up to 9:1) > if we later bring in 3 more LPARs as planned (up to 6 more LP's). When we went from a z9 to a z196, we went from a 3:1 ratio to 5:1. The system still ran, but lpar overhead was huge (regularly around 1%, at times 5%).
> Another concern I have with only 2 CP's is the occasional situation where > some 'looping' condition would dominate a large CP, or half of the box. Or the full box, if your most important lpar with the highest weight and access to all cps gets it into its head to have a memterm loop for every terminating address space in *master*. If that happens, you're dead in the water until that lpar is terminated. Other lpars will run sluggish. No matter if you will have 2 or 3 processors, have a look at your WLM policy. Make sure to only use a minimum amount of service classes (one per importance), because you won't have much leeway with execution velocity goals. On an lpar with a 5:1 ratio, even an exvel of 50% is unattainable in the loved one. And differences of 10% at the same importance won't help and only make more work for WLM. In our sandplex, I went from having lots of service classes to a policy with one service class per importance and put all workloads into that (batch, stc and OMVS - TSO had a response time goal). This allowed the sandbox to get IPL'd and still come up despite being starved for lpar resources. Before that change, a lot of things would time out and an IPL took about an hour (including shutdown). After the new policy, we were done (shutdown and reIPL) in about 15 minutes. Regards, Barbara Nitz ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
