Re: onconfig.ows - MULTIPROCESSOR

Setting it to 0 can improve overall system performance as then when a VP encounters a latched resource it will suspend the current thread and wait for it to be cleared. With MULTIPROCESSOR on the VP will spin for a while before suspending on the assumption that the latch may belong to a thread in another VP so it might free up shortly without suspending the current thread. Setting to one can improve the engine's responsiveness when this is assumption bears out at the expense of overall system performance due to spinning the CPU with no productive result when the cycles could be used by another engine thread or another system process. Personnally, I always set it to one on an SMP platform. Art S. Kagel ----- Original Message ----- From: Rob Phillips <RPhillips@ce-a.com> At: 4/ 8 10:51 > I was talking with IBM today about a problem we were having and we ended up > looking at the onconfig.ows file. Which had the following settings (relavent > to this discussion) > > MULTIPROCESSOR 0 > NUMCPUVPS 2 > SINGLE_CPU_VP 0 > AFF_SPROC 2> AFF_NPROC 0 > > The Machine is a dual processor machine and IBM told me to change > MULTIPROCESSOR to 1. Which is was once but a consultant changed it. I was > reading in "Informix On-Line Dynamic Server Handbook" and it says... > Multiprocessor Machine (MULTIPROCESSOR) > This turns on or off the multiprocessor locking mechanisms, knowsn as "spin > locks," for the instance. If you have a dual-CPU system, try turning this > on and off and test performance. If you have three or more physical CPUs in > the server, set this to "Y." > > What is everyones take on this? Why would setting it to single processor > possibly increase performance in a dual CPU machine when the only thing it > runs is Informix? > > Robert Phillips (rphillips@ce-a.com) > Systems Analyst > Chamberlin Edmonds and Associates (www.ce-a.com) > 404-634-5196 x1261