On Fri, 8 Nov 2019 at 12:59, van Sleeuwen, Berry <[email protected]> wrote:
> Well, the affected LPAR is capped at 6% CPU. And as it turns out a SMAPI > process is active at 5% for one or two minutes, and just in that minute the > MONWRITE machine might have had just a fraction too little CPU time. Oddly > enough we also have a reporting machine processing MONITOR records. Where > MONWRITE simply writes selected records, the reporting machine has some > serious plumbing but that machine had processed all records within time. > (as for CPU usage, MONWRITE uses 0.07% CPU and MONREPT 0.20%, both have a > share ABS 3%.) > If you haven't yet, get the number of logical CPUs down. A problem with very "thin" CPUs is that z/VM is dispatching for a period in wall clock time, but when you're dispatched only 6% of the time, it's likely that your virtual machine gets empty time slices (the moment LPAR dispatches the logical CPU, the time slice has ended already). When that happens a few times, CP puts you in Q3 and gives you larger empty time slices even less frequently. Your ABS 3% may not be worth a lot as that would be based on when all logical CPUs get 100% each. But at least you have the monitor data to figure it out. I think z/OS recommends not to give a logical CPU less than 10% of a CPU worth of weight; such rules of thumb should resonate with your capacity planning friends as well. Rob
