Re: Swap Space
- From: De DBA <dedba@xxxxxxxxxx>
- To: development@xxxxxxxxxxxxxxxxx, Oracle Discussion List <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 26 Mar 2010 12:13:12 +1000
Unfortunately with Oracle processes, the most important such as SMON in the database and OPMN in the oracle app server may seem perfect candidates for this as they tend to be idle most of the time and allocate a lot of memory. Killing these of course is not a good idea, but it does free up memory. It may also kill other vital but usually near-idle processes, causing the OS to become unresponsive.
The oom-killer logs its actions to syslogd, so you can always find a trail showing why the database crashed (assuming that /var is not full and you do log kernel messages).
I am not sure that kswapd pushes up the average load by itself, as this reflects the average number of runnable processes, but I am not a kernel expert by any measure so I may well be wrong here. Incidentally, a load of 40 doesn't strike me as awfully high on 8 (16?) cores. It works out to 2.5-5/core. I've seen dual core machines work quite happily, if not extremely slowly, with loads up to 10-15 per core. At any rate, the number of runnable processes is not a reliable measure for memory usage.
Cheers, Tony On 26/03/10 6:26 AM, Martin Bach wrote:
Hi Bill, just my 0.02 worth. The amount of swap the installer requires is a bit mad with lots of memory like Howard already pointed out. The amount of swap you need depends on your application, bear in mind that if the system runs out of memory and swap it will crash. Before that it will become quite unusable since the kswapd daemon(s) will agressively try to free memory. This process can and will push the load average very high, and if no substantial amount of memory can be freed causing kswapd to sleep again your system is likely to become completely unresponsive to the point where it will have to be rebooted. Just happened to me today-the last stats top reported was a load average of 40 with a 8 dual core opteron box, but I expect it went much higher than that. So if your application is gentle on memory then you only need a little amount of swap (just for that warm fuzzy feeling), but if you know that the box is going to be hit hard you might want to add some extra swap space for peace of mind. Once you did that, tune the application to use less memory-there are plenty of articles out there helping you with that task. Hope that helps, MartinNo the estimates by the installer get a bit mad with a large amount of memory On 25/03/2010, Bill Zakrzewski<bill@xxxxxxxxxxxx> wrote:I am installing Oracle 10.2.0.4.0 on a linux server running RH 5.x with...Thanks in advance, Bill-- http://www.freelists.org/webpage/oracle-l-- Martin Bach OCM 10g http://martincarstenbach.wordpress.com -- http://www.freelists.org/webpage/oracle-l
- Re: Swap Space
- From: Andrew Kerber
- Re: Swap Space