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Home -> Community -> Mailing Lists -> Oracle-L -> Re: Weird database hanging
On 9/18/07, Alex Gorbachev <ag_at_oracloid.com> wrote:
> Could you paste content of /proc/meminfo?
# cat /proc/meminfo
MemTotal: 65907748 kB MemFree: 35313952 kB Buffers: 246220 kB Cached: 25186036 kB SwapCached: 0 kB Active: 26538432 kB Inactive: 886364 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 65907748 kB LowFree: 35313952 kB SwapTotal: 33551744 kB SwapFree: 33551744 kB Dirty: 128 kB Writeback: 0 kB Mapped: 14456204 kB Slab: 673304 kB
HugePages_Total: 0 HugePages_Free: 0 Hugepagesize: 2048 kB
>
> I'm not sure not using huge pages can cause such behavior but 16 GB
> SGA without huge pages on Linux is a killer. Normally, memory is
> managed in small 4k blocks. Each process has it's own page table where
> for each page it has location, permissions, and etc. For shared
> memory, each process will have its own entry in page table but only
> when it first accesses it. What can happen with large SGA, default
> page size and many Oracle processes - page table can actually occupy
> more space than SGA in addition to overhead of on-the-fly allocation
> of entries in page table.
>
> That being said, I'm not sure if that's relevant to your case.
> If you get qualified support engineer than s/he could hopefully see a
> clue there.
My SA said he didn't think it would be an issue. We aren't swapping at all. However at this point we're willing to try ANYTHING.
>
> Another option could be to OS trace the processes with high activity
> during the hang but I'd be careful on production. On the other hand -
> it's not working anyway at those times. :)
You mean like a gdb attach? Oracle Support also asked for this due to my system state dumps being incomplete.
Don.
>
>
> On 9/18/07, Don Seiler <don_at_seiler.us> wrote:
> > 5. We are not using huge pages. My SA says he'll set it up, since it
> > can't hurt now. I'm reading the Puschitz tuning page about it now. I
> > suppose shrinking the SGA or shared pool is always an option.
> >
> > One other difference between old and new servers is that I have
> > enabled the default degree of parallelism on our "warehouse" tables
> > and indexes, and set NOPARALLEL on our frontend objects. On our old
> > hardware it was kind of random which tables or indexes had it enabled
> > and what degree was set. Also our parallel_max_servers is 32, where
> > before it was 8. I don't think it would hurt to bring it down again.
>
>
> --
> Alex Gorbachev, Oracle DBA Brewer, The Pythian Group
> http://www.pythian.com/blogs/author/alex http://www.oracloid.com
> BAAG party - www.BattleAgainstAnyGuess.com
>
-- Don Seiler oracle: http://ora.seiler.us ultimate: http://www.mufc.us -- http://www.freelists.org/webpage/oracle-lReceived on Wed Sep 19 2007 - 08:18:18 CDT
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