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Re: Postgres stopped running (shmget failed)

From: Don Drake <dondrake(at)gmail(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: pgsql-performance(at)postgresql(dot)org
Subject: Re: Postgres stopped running (shmget failed)
Date: 2005-01-26 04:24:15
Message-ID: 6c21003b05012520241a9b3d48@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-performance
On Tue, 25 Jan 2005 11:18:05 -0500, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Don Drake <dondrake(at)gmail(dot)com> writes:
> > This morning I found the postgres not running and the following in my log file:
> 
> > 2005-01-25 01:38:22 FATAL:  could not create shared memory segment:
> > Cannot allocate memory
> > DETAIL:  Failed system call was shmget(key=5432001, size=273383424, 03600).
> > HINT:  This error usually means that PostgreSQL's request for a shared
> > memory segment exceeded available memory or swap space. To reduce the
> > request size (currently 273383424 bytes), reduce PostgreSQL's
> > shared_buffers parameter (currently 32768) and/or its max_connections
> > parameter (currently 40).
> 
> I have seen this happen when the old shmem segment didn't get released
> for some reason, and your kernel settings are such that it won't allow
> creation of two shmem segments of that size at once.  For robustness
> it's probably a good idea to make sure you *can* create two such
> segments at once, but for the moment getting rid of the old one with
> "ipcrm" should be enough to let you restart the postmaster.
> 
>                         regards, tom lane
> 

I was able to just restart it, after the server died and before I
restarted nothing showed up in the ipcs output.

On an unrelated note, the value 273MB seems relatively low to me.  The
DB uses over  27GB for data and indexes, I would think it needs more
shared memory.

Thanks.

-Don

-- 
Donald Drake
President
Drake Consulting
http://www.drakeconsult.com/
312-560-1574

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