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Re: Can SGA be larger than SHMMAX?

From: Matthias Dolder <dolder_at_mail.dec.com>
Date: 1997/02/28
Message-ID: <5f6aqk$fr1$2@mrnews.mro.dec.com>#1/1

In article <5evao4$g48_at_news.eng.octel.com>, bass_at_octel.com says...
>
>oracle (oracle_at_nightmare.com) wrote:
>
>: This is operating system dependent. But I think that on HP you can grab
>: up two
>: segments. I seem to remember something about 3 segments failing for one
>: SGA.
>: I also remember something about a 1gig SHMMAX is the largest it can be.
>: So if you want a two gig SGA you can not go over 1gig for SHMMAX so you
>: would have two segments.
>

On DIGITAL Unix Oracle picks multiple segments if needed. The max number of segments that can be picked by a process are defined by the kernel param SHMSEG. Both SHMMAX and SHMSEG are configurable though i seem to remember, that there was a maximum number of segments Oracle would pick.I would tend to assume that Oracle would work similar on other platforms.

>You can't get a 2 gig SGA. The largest on 7.1.X is 700 MB
>and on 7.3 it is 1.7 GB. This is the limitation on Oracle
>regardless of the platform.

Not exactly true. On AlphaServer Systems running 64-bit DIGITAL Unix, Oracle is fully 64-bitified (VLM64 = 64-bit Very Large Memory Support is the buzzword here). On this platform an Oracle SGA can take virtually any size, though in reality one usually picks one below available physical memory. So on AlphaServer 4100 systems (up to 8 GB memory) and AlphaServer 8400 systems (up to 28 GB memory) it would not be unusal to find Oracle databases with SGA's well beyond 4GB of size [Oracle 64-bit support for DIGITAL Unix became available somewhere in the 7.1.6/7.2.2 timeframe]

rgds
M.Dolder



DIGITAL Equipment Corporation, Switzerland Matthias Dolder

Mail: dolder_at_mail.dec.com

...speaking for myself, not DIGITAL...

>
>-Bass Chorng
Received on Fri Feb 28 1997 - 00:00:00 CST

Original text of this message

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