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#1 (**permalink**) 02-25-2008, 01:29 AM

We have 64 bit Hp-ux. RAM on my server is 4gb.If I set SHMMAX to 1 Gb
and I have 3 databases on the server. What is the limit of SGA for all
the databases? Is it 1 GB for all or 1 Gb is the limit for one database?

#2 (**permalink**) 02-25-2008, 01:30 AM

On 7 Jan 2006 06:58:05 -0800, "nhk" <chughhk@gmail.com> wrote:

>We have 64 bit Hp-ux. RAM on my server is 4gb.If I set SHMMAX to 1 Gb
>and I have 3 databases on the server. What is the limit of SGA for all
>the databases? Is it 1 GB for all or 1 Gb is the limit for one database?

If I recall correctly SHMMAX limits the size of a single shared memory
segment. However, shared memory is still paged.

Oracle recommends that the total size of all SGAs on a server
shouldn't be bigger than about one third of physical RAM.
This is for obvious reasons, because you will force the server to page
if you increase the SGAs beyond reasonable limits.
That said, you would better tune applications, than trying to get the
server on it's knees.

--
Sybrand Bakker, Senior Oracle DBA

#3 (**permalink**) 02-25-2008, 01:30 AM

On Sat, 07 Jan 2006 06:58:05 -0800, nhk wrote:

> We have 64 bit Hp-ux. RAM on my server is 4gb.If I set SHMMAX to 1 Gb
> and I have 3 databases on the server. What is the limit of SGA for all
> the databases? Is it 1 GB for all or 1 Gb is the limit for one database?

The Oracle database installation document for *nix does a decent job of
defining this - search for SHMMAX and SHMMNI in the prerequisites chapter.

--
Hans Forbrich
Canada-wide Oracle training and consulting
mailto: Fuzzy.GreyBeard_at_gmail.com
*** Top posting [replies] guarantees I won't respond. ***

#4 (**permalink**) 02-25-2008, 01:38 AM

HI Sybrand and others,

> If I recall correctly SHMMAX limits the size of a single shared memory
> segment. However, shared memory is still paged.

If we set` lock_sga parameter in init.ora willshared memory still be
paged?

Thanks

Sybrand Bakker wrote:
> On 7 Jan 2006 06:58:05 -0800, "nhk" <chughhk@gmail.com> wrote:
>
> >We have 64 bit Hp-ux. RAM on my server is 4gb.If I set SHMMAX to 1 Gb
> >and I have 3 databases on the server. What is the limit of SGA for all
> >the databases? Is it 1 GB for all or 1 Gb is the limit for one database?
>
> If I recall correctly SHMMAX limits the size of a single shared memory
> segment. However, shared memory is still paged.
>
> Oracle recommends that the total size of all SGAs on a server
> shouldn't be bigger than about one third of physical RAM.
> This is for obvious reasons, because you will force the server to page
> if you increase the SGAs beyond reasonable limits.
> That said, you would better tune applications, than trying to get the
> server on it's knees.
>

> --
> Sybrand Bakker, Senior Oracle DBA

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