Re: 3GB RAM usage by Oracle

don_at_burleson.cc (Don Burleson) wrote in message news:<998d28f7.0408241456.4303efc4_at_posting.google.com>...
> > So I was thinking rest of the RAM (1.5GB) is not being utilised. Hence I
> > posted the question.
>
> Yes, you are wasting RAM, and this is very common on 32-bit Oracle
> Windows databases, especially servers with 8 gig RAM and a HWM PGA
> uasgae of less than 500 meg.
>
> There are two solutions used by most shops. You have two choices, 4GT
> or AWE. AWE is best and you can use all of the RAM for Oracle.
>
> In my experience the increased data caching can make a huge difference
> and for a dedicated Windowsz server you only need to reserve 20% of
> the RAM for the OS, and save the rest for SGA and PGA.
>
> 4GT:
>
> - In Windows NT Server v4.0 EE, 4 gig RAM Tuning (4GT) was added which
> allows SGA up to 3 gig of memory as opposed to the standard 2 gig.
> (Yes, 4GT = 3 gig)
>
> - Gives Oracle up to 50% more memory. (but still not enough)
>
> - For larger systems 64-bit Oracle allows up to 512 gig SGA sizes.
>
> - All that's needed is an added boot.ini switch -- /3GB
>
> AWE:
>
> - AWE (Address Windowing Extension) - Allows 32-bit Windows Oracle to
> have up to 64 gig of database buffers.
>
> - Available after Oracle8i (8.1.6).
>
> - Moves database buffers out of the 3GB address space "above the
> line", leaving low-memory RAM for more connections, larger sort areas,
> etc...
>
> - The Win32 AWE (Address Windowing Extension) calls are used which
> provide a fast map/unmap interface to "above the line" RAM.
>
> - When running on a machine with >16GB of RAM, Oracle can either use
> the 4GT feature or the memory above 16GB, but not both. This is a
> Windows limitation.
>
> - From the Oracle 3 gig address space, we allocate space for a
> ?window' onto the whole of the db buffers.
>
> - The size of this window is user-configurable.
>
> - The larger the window, the more buffers are quickly available,
> however the larger the window, the less space there is for other
> memory structures like shared pool, connections, PGAs, etc.
>
> INSTALLING AWE:
>
> - Set use_indirect_data_buffers=true
>
> - Set AWE_WINDOW_SIZE in the registry to the number of bytes of
> address space to use for your window onto extended memory. The
> default is 1GB.
>
> - Increase db_cache_size to a higher value up to available memory

Don,

One thing to add:

"large" memory support was broken for win32 in 8.1.7.3.x and 8.1.7.4.x.
It worked in 9.2.0.3, 9.2.0.4.

If you were running /3GB against 8.1.7.2.6 - you were in for quite a surprise when the 8.1.7.3.0 patchset was applied.

I've got the scars to prove it - ask MA.

-bdbafh Received on Tue Aug 24 2004 - 21:11:13 CDT