RE: Solaris 10 and Oracle 10g - swap space problem

From: Crisler, Jon <>
Date: Wed, 29 Jul 2009 10:41:27 -0400
Message-ID: <56211FD5795F8346A0719FEBC0DB067504A7BB78_at_mds3aex08.USIEXCHANGE.COM>

I never use lock_sga - its one of those things that I had the feeling should only be used in special cases, which I never ran into.  

From: [] On Behalf Of Mathias Magnusson
Sent: Wednesday, July 29, 2009 2:42 AM
To: Crisler, Jon
Subject: Re: Solaris 10 and Oracle 10g - swap space problem  

It makes the reservation, but if you have memory it would not use it. You just end up wasting some disk for swap you'll never use. If you increase Swap above 64 GB, does it work? Why would it crawl now? Fail for some DBs, but if you never use Swap, then allocation of it should not impact performance. Look at memory pressure to make sure the server never does pagescans - sr column i vmstat - of any real magnutude (over 200 is probably not desireable in production).  

Also, would the parameter lock_sga have any effect in Solaris? I've never tested it, but in theory it would pin SGA in real memory and never let it go to Swap, which also would mean that it should not reserve it. It's one of those parameter I've meant to play with, but I've never gotten around to actually test the effect.  


On Wed, Jul 29, 2009 at 1:31 AM, Crisler, Jon <> wrote:

On Solaris 10, when I start my databases, I see my swap space usage increase in a one for one ratio with memory utilization. System has 64gb of memory. If I start up a 4gb database, I see 4gb of real memory used and 4gb of swap space used up as well (as shown by top, swap -l, swap -s etc.). This is purely a Oracle database server, and /etc/system and projects / resource controls seem to be set up, so I do not understand why swap is being touched. If I stop all oracle processes, swap drops down to about 100 Mb used.  

I have taken great pains to make sure that NO swap is being used, yet any little allocation of Oracle gets tossed into swap. I don't know where to look after this- I would have suspected /etc/system or resource control / projects to be at fault, or /etc/security (ulimits) but everything looks ok. The system has 64g real, and about 54 gb swapif  I get close to 54gb memory allocated oracle will return out of memory errors.. Needless to say the system crawls.  

What am I overlooking ? TOP and swap -s / swap -l agree so its not a TOP anomaly  

Example from TOP - I have 20g free, so why so much used in swap ?  

load averages: 0.64, 0.57, 0.46

1073 processes:1071 sleeping, 2 on cpu

CPU states: 98.3% idle, 1.2% user, 0.5% kernel, 0.0% iowait, 0.0% swap

Memory: 64G real, 20G free, 40G swap in use, 17G swap free  

   PID USERNAME LWP PRI NICE SIZE RES STATE TIME CPU COMMAND   1997 oracle 1 39 0 4376K 2592K cpu/50 0:02 0.04% top

  3454 oracle 1 52 0 16G 16G cpu/32 0:00 0.03% oracle

  3456 oracle 1 24 0 16G 16G sleep 0:00 0.03% oracle

 18589 oracle 1 59 0 16G 16G sleep 0:13 0.02% oracle  

Swap -s

total: 39170184k bytes allocated + 2262264k reserved = 41432448k used, 18017608k available  

Received on Wed Jul 29 2009 - 09:41:27 CDT

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