Re: Oracle creates multiple shared memory segments despite SGA < SHMMAX
From: ddf <oratune_at_msn.com>
Date: Fri, 6 Mar 2009 05:58:57 -0800 (PST)
Message-ID: <cd356128-c100-4ed1-9873-133b24135c83_at_17g2000vbf.googlegroups.com>
On Mar 5, 4:15 pm, ca111..._at_gmail.com wrote:
> This is new installation of 10.2.0.4 on HP-UX 11.23 Itanium.
> HP-UX kernel parameter SHMMAX is 10G,
> Oracle parameter SGA_MAX_SIZE set to 8G.
>
> On startup Oracle creates 4 shared memory segments, size in bytes:
> 4064346112
> 4076863488
> 488710144
> 20480
>
> Any idea why?
>
> Yes I know that it *should* run OK with multiple shared memory
> segments,
> and I am aware that it is normal to create segments with different
> size
> (Metalink Note 15566.1). Still I would prefer to have one segment, not
> 4.
>
> There is only one instance on this server, there is no other software
> that uses IPC (Tuxedo, etc), Oracle started immediatelly after server
> reboot.
>
> The only kernel parameter set to 4G is MAXDSIZ_64BIT. As far as I
> understand
> it shouldn't affect sizing of shared memory segments.
Date: Fri, 6 Mar 2009 05:58:57 -0800 (PST)
Message-ID: <cd356128-c100-4ed1-9873-133b24135c83_at_17g2000vbf.googlegroups.com>
On Mar 5, 4:15 pm, ca111..._at_gmail.com wrote:
> This is new installation of 10.2.0.4 on HP-UX 11.23 Itanium.
> HP-UX kernel parameter SHMMAX is 10G,
> Oracle parameter SGA_MAX_SIZE set to 8G.
>
> On startup Oracle creates 4 shared memory segments, size in bytes:
> 4064346112
> 4076863488
> 488710144
> 20480
>
> Any idea why?
>
> Yes I know that it *should* run OK with multiple shared memory
> segments,
> and I am aware that it is normal to create segments with different
> size
> (Metalink Note 15566.1). Still I would prefer to have one segment, not
> 4.
>
> There is only one instance on this server, there is no other software
> that uses IPC (Tuxedo, etc), Oracle started immediatelly after server
> reboot.
>
> The only kernel parameter set to 4G is MAXDSIZ_64BIT. As far as I
> understand
> it shouldn't affect sizing of shared memory segments.
You're looking in the wrong place, I think, since this server could be configured for non-uniform memory access (NUMA) which would create multiple shared memory segments. Possibly you should ask your Sys Admin how the box is built; he or she may have the answers you seek.
David Fitzjarrell Received on Fri Mar 06 2009 - 07:58:57 CST