Jay,
My column counting skills might be off, but it looks
like the 'sr' stat is 0 most of the time, and scan
rate is the stat that I use to see if a machine is
memory starved.
Priority paging is a very good idea, but you'll
probably see even more benefit if you can mount your
oracle file systems as direct io
hth
connor
- Rich Holland <holland_at_guidancetech.com> wrote: >
Jay,
>
> My understanding is that the PGA is contained within
> the SGA, and that
> shmmax is the "maximum size of a single shared
> memory segment". If you
> set shmmax to 256MB and configure 1GB SGA, you
> should see it allocate 4
> shared memory segments for that purpose. Some Unix
> variants have
> limitations on the number of shared memory segments
> which can either be
> created (AIX) or simultaneously accessed (HP-UX). I
> haven't done much
> with Sun in the last few years so don't specifically
> know of the Solaris
> limitations, but I'm sure there is probably
> something there to consider.
> That's typically why you want to set shmmax as high
> as you realistically
> can -- to reduce the NUMBER of segments you need to
> allocate for shared
> memory.
>
> Your sysadmin also mentions turning on "priority
> paging" to give the
> user processes access to the memory before the file
> cache (aka buffer
> cache). Again I'm not sure about Solaris, but AIX
> and HP-UX both ship
> with their buffer cache set to something like 10% -
> 20% of total memory
> by default, which is a pretty good guess for a
> generic system when the
> vendor has no idea what you'll be using it for
> specifically... however,
> for large Oracle systems, I typically tune this back
> a bit, depending on
> the memory in the system. Normally something in the
> 2-8% or 3-10% range
> is sufficient. Remember, Oracle does all it's own
> buffering via
> DB_BLOCK_BUFFERS so doesn't really need to rely on
> the system buffer
> cache, even using filesystems (of course, raw
> devices completely bypass
> the system buffer cache).
>
> You might want to see what he's got the two
> parameters set to which
> control the size of the system buffer cache;
> sometimes reducing that
> will help quite a bit with paging/swapping.
>
> Rich
>
> > -----Original Message-----
> > From: root_at_fatcity.com [mailto:root_at_fatcity.com]
> On Behalf Of Miller,
> Jay
> > Sent: Saturday, November 23, 2002 1:49 PM
> > To: Multiple recipients of list ORACLE-L
> > Subject: Do user processes apply against shmmax
> limit?
> >
> > Hi everyone,
> >
> > I was always under the impression that the only
> concern with shmmax
> was
> > that
> > it be large enough for the SGA to fit into it. One
> of my System
> > Administrators has just told me that the
> individual user processes
> (i.e.,
> > the PGA since we're not using multi-threaded
> server) get added to the
> SGA
> > and if that SGA + user processes > shmmax the
> system will start
> swapping.
> >
> > I haven't found anything to specifically address
> this issue on
> Metalink so
> > I
> > though I'd throw it open. We've started
> experiencing system slowdown
> and
> > he
> > says that increasing shmmax could resolve it. I'm
> skeptical (he also
> > suggested increasing SGA to decrease swapping
> which I told him in no
> > uncertain terms was nonsense).
> >
> > If anyone has a link to a note or white paper I'd
> appreciate that too.
> >
> > I've appended his email at the bottom. This
> slowdown seems to occur
> even
> > when there's virtually on oracle activity so I'm
> suspecting some other
> > cause.
> >
> > Thanks,
> > Jay Miller
> >
> >
> >
> >
> > nycsun1 and njsun7 has 6 GB of memory and only 2
> GB of share memory.
> This
> > morning nycsun1 was very slow and I noticed that
> there was lots of
> > swaping.
> > see vmstst and iostat below in red:
> >
> > procs memory page disk
> faults
> cpu
> > r b w swap free re mf pi po fr de sr s2 s4
> s4 sd in sy cs
> us
> > sy
> > id
> > 0 0 23 4366736 97528 1 2186 16 12 12 95520 0 0 0
> 0 0 1104 3330 974
> 11
> > 8
> > 81
> > 0 0 23 4365992 96056 1 451 16 24 52 85968 3 0 0
> 0 0 935 847 416
> 3
> > 1
> > 96
> > 0 0 23 4364712 95512 2 310 36 24 492 85968 68 0 0
> 0 0 1036 2183 670
> 13
> > 4
> > 84
> > 0 0 23 4361568 95488 9 2264 0 76 964 95520 136 0
> 0 0 0 979 4065 607
> 12
> > 6
> > 82
> > 0 0 23 4362384 96080 1 6 4 8 8 77376 0 0 0
> 0 0 975 465 457
> 2
> > 1
> > 97
> > 0 0 23 4361944 95712 4 730 92 48 532 95520 64 0 0
> 0 0 1040 1859 734
> 8
> > 3
> > 89
> > 0 0 23 4360424 95480 4 41 36 40 100 77376 7 0 0
> 0 0 986 1250 542
> 6
> > 0
> > 94
> > 0 0 23 4361304 96096 3 264 76 36 88 88496 7 0 0
> 0 0 1037 942 665
> 5
> > 3
> > 92
> > 0 0 23 4359680 95784 2 449 4 28 84 95520 8 0 0
> 0 0 922 1047 374
> 4
> > 1
> > 95
> > 0 0 23 4359936 95464 2 544 4 20 332 95520 44 0 0
> 0 0 931 1095 384
> 2
> > 2
> > 96
> >
> > /s w/s kr/s kw/s wait actv wsvc_t asvc_t %w
> %b device
> > 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
> 0 0 c2t6d0
> > 0.0 34.5 0.0 270.0 0.2 13.8 6.7 399.5
> 6 44 c5t12d0 --
> swap
> > disk
> > 0.0 34.5 0.0 270.0 0.5 10.7 15.5 309.4
> 18 39 c5t13d0 --
> swap
> > disk
> >
> >
> > This shows that the system is not effectively
> using memory. I suggest
> > increasing the share memory to 4 GB so that DBAs
> can increase their
> memory
> > usage. Also set priority paging on. Priority
> paging will give
> application
> > first priority then free memory will be allocated
> to file cache(
> Solaris
> > 2.6
> > and 7. Solaris 8 is set dynamically).
> >
> > * ORACLE CONFIGS
> > set shmsys:shminfo_shmmax =2048000000 --
> increase to 4096000000
> > set shmsys:shminfo_shmmin=1
> > set shmsys:shminfo_shmmni=300
> > set shmsys:shminfo_shmseg=30
> > set semsys:seminfo_semmap=500
> > set semsys:seminfo_semmni=200
> > set semsys:seminfo_semmns=2000
> > set semsys:seminfo_semmsl=1000
> > set semsys:seminfo_semmnu=500
> > set semsys:seminfo_semume=150
> >
> >
> >
> > --
> > Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> > --
> > Author: Miller, Jay
> > INET: JayMiller_at_TDWaterhouse.com
> >
> > Fat City Network Services -- 858-538-5051
> http://www.fatcity.com
> > San Diego, California -- Mailing list and
> web hosting services
> >
>
> > To REMOVE yourself from this mailing list, send an
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> > to: ListGuru_at_fatcity.com (note EXACT spelling of
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> --
> Please see the official ORACLE-L FAQ:
> http://www.orafaq.com
> --
> Author: Rich Holland
> INET: holland_at_guidancetech.com
>
> Fat City Network Services -- 858-538-5051
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Received on Fri Nov 29 2002 - 09:08:40 CST