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Re: Oracle on Windows 2000 AS with /3GB flag

From: Yavor Ivanov <>
Date: Tue, 17 Jul 2007 17:56:24 +0300
Message-ID: <>

	The switch is no relevant to 64 bit platforms.
	On 32 bit platforms, any process can address 4 GB memory (this is 2^32 bytes), but has the right to use only the lower 2 GB (minus some kylobytes at the start and the end, for boundery checking). The upper 2 GB are reserved for the OS.
	The the /3GB switch changes this ratio to 3 GB user addressable space and 1 GB for the OS. This is address space per process, no actually consumed memory - even Notepad has the same address space, private for it's process.
	I have used this switch on many servers without any issue.
	On 64 bit platforms any process can address much more memory. So the switch does not work - it is not needed.

Yavor Ivanov
Senior Database Expert
Stemo Ltd

On Tue, 17 Jul 2007 02:51:58 +0300, William Wagman <> wrote:

> Allen,
>Does this hold true for 64-bit Windows as well? Until seeing this thread
> I was unaware of the /3GB switch available for windows. It sounds
> analogous to compiling in the hugemem kernel in Linux. Or are the two
> unrelated? On Technet so far the only document I have found is the
> 32-bit Oracle Database Platform Guide, chapter 1. Can you point out a
> good source of information on this please.
> Bill Wagman
> Univ. of California at Davis
> IET Campus Data Center
> (530) 754-6208
> ________________________________
> From:
> [] On Behalf Of Allen, Brandon
> Sent: Monday, July 16, 2007 3:07 PM
> To:;
> Subject: RE: Oracle on Windows 2000 AS with /3GB flag
> I always use the /3G flag on all Windows database servers - for both
> Oracle and SQL Server. I've used it several times on different
> combinations of Windows, SQL & Oracle versions and never had any
> problems.
> Brandon
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Received on Tue Jul 17 2007 - 09:56:24 CDT

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