/3GB Switch

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Satwinder - 22 Jul 2006 07:18 GMT

I have 2 instance of SQL Server 2000 Enterprise ED in active/active 2 node
cluster. Each node box have 8GB RAM.
If i enable /3GB switch on each node. In case of failover, when both the sql
instances are running on a single node, will both node will take 3GB each OR
total of 3GB have to be shared among each node.

Thanks,

Reply to this Message

Tom Moreau - 22 Jul 2006 17:02 GMT

Each instance will take up to 3GB.

Signature

Tom

----------------------------------------------------
Thomas A. Moreau, BSc, PhD, MCSE, MCDBA
SQL Server MVP
Toronto, ON Canada

Reply to this Message

Linchi Shea - 22 Jul 2006 23:21 GMT

/3GB switch affects virtual memory only. Per Microsoft documentation, "The
/3GB switch allocates 3 GB of virtual address space to an application that
uses IMAGE_FILE_LARGE_ADDRESS_AWARE in the process header. This switch allows
applications to address 1 GB of additional virtual address space above 2 GB."
(http://www.microsoft.com/whdc/system/platform/server/PAE/PAEmem.mspx)

SQL Server is one of these applications that have the mentioned image header
flag. And since we are talking about virtual memory of physical memory, 3GB
of the virtual address space of one process is never shared with that of
another process.

Linchi

> I have 2 instance of SQL Server 2000 Enterprise ED in active/active 2 node
> cluster. Each node box have 8GB RAM.
[quoted text clipped - 3 lines]
>
> Thanks,

Reply to this Message

Mike Hodgson - 31 Jul 2006 03:36 GMT

Be careful about using the terms "virtual memory" and "virtual address
space", which are different things and not interchangeable terms. The
/3GB switch affects the _virtual address space_ of every application,
which may or may not include some amount of virtual memory (ie. one or
more system paging files resident on disk). The virtual address space
of an application, SQL Server included, is made up of both physical
memory and virtual (or "mapped") memory.

--
*mike hodgson*
http://sqlnerd.blogspot.com

>/3GB switch affects virtual memory only. Per Microsoft documentation, "The
>/3GB switch allocates 3 GB of virtual address space to an application that
[quoted text clipped - 19 lines]
>>Thanks,
>>

Reply to this Message

Satwinder - 24 Jul 2006 18:41 GMT

Is it neccesary to change the memory configuration from Dynamic to max.
memory one, when /3GB switch is used and both instances are running on same
node.

thanks,

> I have 2 instance of SQL Server 2000 Enterprise ED in active/active 2 node
> cluster. Each node box have 8GB RAM.
[quoted text clipped - 3 lines]
>
> Thanks,

Reply to this Message

Satwinder - 28 Jul 2006 14:37 GMT

When /3GB is enabled on server running 2 instances of SQL server having 8GB
of Physical RAM, is it necessary to change memory configuration from dynamic
to Max memory to 3GB.

Will /3GB in any chance cause the SQL server to use more than 3GB of memory.

Pls advice on this asap so that i can go ahead with the chage ????

> Is it neccesary to change the memory configuration from Dynamic to max.
> memory one, when /3GB switch is used and both instances are running on same
[quoted text clipped - 9 lines]
> >
> > Thanks,

Reply to this Message

Tom Moreau - 28 Jul 2006 22:49 GMT

As long as you're not using AWE, each instance won't go above 3GB., so you
won't need to set the max server memory.

Signature

Tom

----------------------------------------------------
Thomas A. Moreau, BSc, PhD, MCSE, MCDBA
SQL Server MVP
Toronto, ON Canada
.

> Is it neccesary to change the memory configuration from Dynamic to max.
> memory one, when /3GB switch is used and both instances are running on
[quoted text clipped - 13 lines]
> >
> > Thanks,

Reply to this Message