Esteemed colleges: A topic that has occasionally graced IBM-MAIN for over a decade is capping, and technology keeps changing so as to adjust the answer. Having newer technology, we now have a handful of capping issues, and IBM is coming up with new microcode (about now as I recall) to manage groups of LPARs under an umbrella cap, which someone may have beta tested by now. We are planning soft capping only, no hardware capping, and wonder about its effects on our new hardware and reconfigured systems.
Ordinarily, as PR/SM dispatches CPs to LPARs, a Logical CP may have a task dispatched to it, but beneath it, it has no physical CP. Milliseconds later, the CP may well be back and the task actually runs. But when we had our 2064-104 and it's cap kicked in, the CP was gone for awhile, not for a few seconds at a time but for minutes, and response time suffered noticeably. It seems that, with fewer engines, and a steeper climb to exceed the cap, an engine may be gone for quite awhile, compared to a several-engine system whose cap is closer to machine capacity. It was also being capped during lunch time, when customarily our usage dropped anyway, so we did not logically need that 4th CP. But the distinct impression we got was that MVS was not aware that one LCP had become only a phantom, and MVS had not varied a CP offline, but instead continued to attempt to dispatch work to it. 1. Given that an over-busy LPAR looses one or more CPs from being dispatched for more than milliseconds, does MVS know that the CP is gone? (Currently we have a 2094-S08.) As the MVS scheduler dispatches, does a 4-engine LPAR's MVS treat the situation internally as if it still had 4 engines, while one of them is out-to-lunch due to capping, or is MVS instead informed, varies the CP offline internally, and dispatches its work on just the remaining 3 CPs? It would seem that, if the situation has become significant enough for an engine to be offline long enough (minutes to an hour) but without MVS's knowledge, then it might be more beneficial if (perhaps by automation) an engine was officially varied offline, allowing work that is dispatched to actually run, rather than having the TCB imagine that it is going to run on a LCP whose PCP is not there anymore. Of course the follow-up question wonders whether the now-3-CP environment will have one of its PCPs taken away as PR/SM figures that it has to actually pinch somewhere to fix its average? Observations? And how has the group-of-capped-LPARs worked? 2. What happens in the case of a smaller machine that has only 1 CP and one LPAR in the first place? An ISV penalty box usually is not well-powered, and seldom has additional LPARs running in it. Can an 8 MSU single-cp box be capped at 2 MSUs? Does it require additional dummy or real LPARs, defined but not running, whose purpose or function is to let WLM operate without using additional MSUs? What if one of the present box's extra CPs (2096-S07) was turned into an IFL? Would that suffice for WLM to keep a 4HRA lid of 2 MSUs on the general purpose CP? In the past, it was sometimes true that no actual capping could occur without at least another LPAR being defined. Again, soft capping is our goal, to allow for workload spikes, but for the IBM billing process, to restrain the usage to 2 MSUs. Thanks for your observations, Rick Rick Rodie USG Corp [EMAIL PROTECTED] 312-436-5578 Confidentiality Notice: This email is intended for the sole use of the intended recipient(s) and may contain confidential, proprietary or privileged information. If you are not the intended recipient, you are notified that any use, review, dissemination, copying or action taken based on this message or its attachments, if any, is prohibited. If you are not the intended recipient, please contact the sender by reply email and destroy or delete all copies of the original message and any attachments. Thank you. ---------------------------------------------------------------------- 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
