Any gotchas for STMM
in [DB2]
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From: Serge Rielau on 21 Jun 2010 14:48 Mark, How about sending a note to Adam with your company affiliation so he can drill down on the issues your company had on his own? That's not much work for you and saves Adam from divining up what might have been wrong in your case. Cheers Serge -- Serge Rielau SQL Architect DB2 for LUW IBM Toronto Lab
From: Mark A on 21 Jun 2010 17:19 "Serge Rielau" <srielau(a)ca.ibm.com> wrote in message news:889qf6Fo7lU1(a)mid.individual.net... > Mark, > > How about sending a note to Adam with your company affiliation so he can > drill down on the issues your company had on his own? > That's not much work for you and saves Adam from divining up what might > have been wrong in your case. > > Cheers > Serge Ok. I will do that.
From: Frederik Engelen on 22 Jun 2010 06:04 Mark, I'm not going into more detail regarding the whole STMM thing except saying that it works pretty well for us, as long as we fix the instance_memory parameter. What I am curious for is why you would only assign 50% of server memory to the bufferpools. Give or take a few gigs for OS and database housekeeping, that would leave half of your server memory unused, no? Kind regards, Frederik
From: Mark A on 22 Jun 2010 08:45 "Frederik Engelen" <engelenfrederik(a)gmail.com> wrote in message news:cad1fcee-4f54-4f83-8d8c-e2799e2bb530(a)d37g2000yqm.googlegroups.com... > Mark, > > I'm not going into more detail regarding the whole STMM thing except > saying that it works pretty well for us, as long as we fix the > instance_memory parameter. > > What I am curious for is why you would only assign 50% of server > memory to the bufferpools. Give or take a few gigs for OS and database > housekeeping, that would leave half of your server memory unused, no? > > Kind regards, > > Frederik I would normally assign more than 50% of total system memory to buffepools. But most DB2 novices used the defaults in 8.2 or very small amounts which are closer to 1% or less, so 50% would be a huge improvement over that. One might go as high as 75-80% depending on total server memory and other factors, but in most situations one would not notice much difference between 50% and 75%. Also, at least with Linux, DB2 servers do tend to run out of memory for various reasons. The documenation of Linux kernel parameters is someitmes contradictory in the manuals, or sometimes has been completely lacking. For example, although not mentioned anywhere in the official doc, some Redbooks recomend: vm.swappiness=0 (default for RHEL is 60) vm.dirty_ratio=10 vm.dirty_background_ratio=5 Recommendations for SHMALL have been all over the place, from 90% of system memory, 100% of system memory, to now apparently 200% of system memory. Any changes to Linux Kernel Parm recommendations should be a Hiper doc APAR and not slipstreamed in the InfoCenter. I noticed in the 9.7 Fixpack 2 Info Center webpages, they are now enforcing Linux kernel parms automatically that were not enfoced even in 9.7.1. This is obviously to fix the problems that customers have been experiencing with memory on DB2 Linux systems, especially with STMM activated.
From: Mark A on 22 Jun 2010 09:13
"Mark A" <noone(a)nowhere.com> wrote in message news:hvqba4$h5f$1(a)news.eternal-september.org... > Recommendations for SHMALL have been all over the place, from 90% of > system memory, 100% of system memory, to now apparently 200% of system > memory. Any changes to Linux Kernel Parm recommendations should be a Hiper > doc APAR and not slipstreamed in the InfoCenter. Here is where it states SHMALL should be 200% (and now enfoced that way in 9.7.2). "2 * <size of RAM in bytes> (setting is in 4K pages)" http://publib.boulder.ibm.com/infocenter/db2luw/v9r7/topic/com.ibm.db2.luw.qb.server.doc/doc/c0057140.html Here is where it states that SHMALL should be 90%: "...whereas the parameter SHMALL should be set to 90% of the available memory on the database server." http://publib.boulder.ibm.com/infocenter/db2luw/v9r7/topic/com.ibm.db2.luw.admin.perf.doc/doc/c0054689.html Is anyone at IBM awake these days? |