MS SQL Server - Does the /PAE /3GB switch order matter in the boot.ini?

Author

Does the /PAE /3GB switch order matter in the boot.ini?

JTT

2006-02-25, 9:26 am

I have a vendor trying to tell me that the order of the switches in the
boot.ini will make a difference for allocating memory to SQL Server. We are
running Windows 2003 Enterprise Server and SQL 2000 Enterprise Server with
7GB of RAM. We have entered in the /pae /3GB switches and they changed them
to read /3GB /PAE claiming that would fix our problem.

However my understanding is that these two switches are non-related so the
order should not matter. My understanding is the /PAE basically enables your
OS to utilize more than 4GB and the /3GB is used so that applications like
SQL will utilize 3GB of the first 4 instead of the 2 that it would standard
leaving 1GB for the Kernal/Windows.

Not to mention that I do not believe there is a difference in the /pae
(lowercase) and /PAE (upper) that they claim. Does it matter in which order
the /PAE and /3GB switches are listed in the boot.ini or are they just
grabbing at straws?

Thanks in advance,

JTT

Mike Hodgson

2006-02-25, 9:27 am

They're full of ____ (fill in the blank).

/PAE & /3GB aren't directly related but they do both deal with memory
allocation, as you've outlined. Your understanding of /PAE is correct
(it enables physical address extensions, which allows the OS to address
more than the 32bit addressing maximum of 4GB). /3GB would be better
described as allowing applications, such as SQL Server, to reserve only
1GB of RAM for kernel mode and the rest for user mode (when the virtual
address space is only 4GB, which is typical, then "the rest" equates to
3GB hence the name of the switch but when the OS can address more than
4GB through memory extension code the user mode address space will be
more than 3GB (IMHO Microsoft should have called the switch /1GB)).

It doesn't matter if they're upper case, lower case or mixed case (it's
case insensitive). It doesn't matter if you specify /PAE first or /3GB
first (order is unimportant - for example, I've got a DR server using
8GB RAM with boot.ini switches "/pae /3gb", all lower case with pae first).

If you have a choice of vendors I'd either be asking for someone better
qualified within their company who would actually do a little research
rather than just trying to pull the wool over your eyes, or I'd be
saying goodbye to them and looking for a quality vendor with at least 1
employee who had worked with Windows Server for more than 2 years. If
you have no choice of vendor, I commiserate and offer my condolences.

NB/ In Windows Server 2003 you also have the option of using the /userva
switch, rather than /3GB, that allows finer granularity of the user mode
memory allocation.

Good luck.

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

JTT wrote:

>I have a vendor trying to tell me that the order of the switches in the
>boot.ini will make a difference for allocating memory to SQL Server. We are
>running Windows 2003 Enterprise Server and SQL 2000 Enterprise Server with
>7GB of RAM. We have entered in the /pae /3GB switches and they changed them
>to read /3GB /PAE claiming that would fix our problem.
>
>However my understanding is that these two switches are non-related so the
>order should not matter. My understanding is the /PAE basically enables your
>OS to utilize more than 4GB and the /3GB is used so that applications like
>SQL will utilize 3GB of the first 4 instead of the 2 that it would standard
>leaving 1GB for the Kernal/Windows.
>
>Not to mention that I do not believe there is a difference in the /pae
>(lowercase) and /PAE (upper) that they claim. Does it matter in which order
>the /PAE and /3GB switches are listed in the boot.ini or are they just
>grabbing at straws?
>
>Thanks in advance,
>
>JTT
>
>

Vincent Xu [MSFT]

2006-02-25, 9:27 am

Hi JTT,

Thanks Mike's excellent explanation and you may also refer to:

833721 Available switch options for the Windows XP and the Windows Server
2003 Boot.ini files
http://support.microsoft.com/defaul...kb;EN-US;833721

Actually I think this problem is foreign to SQL Server but it is related to
Widows Server 2003. I think Windows Server 2003 Newsgroup would be a more
approprate place for such issue.

Have a good day~

Best regards,

Vincent Xu
Microsoft Online Partner Support

Get Secure! - www.microsoft.com/security

When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.

This posting is provided "AS IS" with no warranties, and confers no rights.

--------------------[color=darkred]
are[color=darkred]
with[color=darkred]
them[color=darkred]
the[color=darkred]
your[color=darkred]
like[color=darkred]
standard[color=darkr
ed]
order[color=darkred]

JTT

2006-02-25, 9:27 am

Mike-

Thanks. I did not believe so and I couldn't find anything that said so
either so I thought I should post and make sure there wasn't something I
missed. Ufortunately we have no choice in vendor at this point, we made the
change in the INI to appease them but I wanted to verify so that when I send
my manager and them an email this morning I had someone else saying what I've
already told them.

Thanks again

JTT

"Mike Hodgson" wrote:

> They're full of ____ (fill in the blank).
>
> /PAE & /3GB aren't directly related but they do both deal with memory
> allocation, as you've outlined. Your understanding of /PAE is correct
> (it enables physical address extensions, which allows the OS to address
> more than the 32bit addressing maximum of 4GB). /3GB would be better
> described as allowing applications, such as SQL Server, to reserve only
> 1GB of RAM for kernel mode and the rest for user mode (when the virtual
> address space is only 4GB, which is typical, then "the rest" equates to
> 3GB hence the name of the switch but when the OS can address more than
> 4GB through memory extension code the user mode address space will be
> more than 3GB (IMHO Microsoft should have called the switch /1GB)).
>
> It doesn't matter if they're upper case, lower case or mixed case (it's
> case insensitive). It doesn't matter if you specify /PAE first or /3GB
> first (order is unimportant - for example, I've got a DR server using
> 8GB RAM with boot.ini switches "/pae /3gb", all lower case with pae first).
>
> If you have a choice of vendors I'd either be asking for someone better
> qualified within their company who would actually do a little research
> rather than just trying to pull the wool over your eyes, or I'd be
> saying goodbye to them and looking for a quality vendor with at least 1
> employee who had worked with Windows Server for more than 2 years. If
> you have no choice of vendor, I commiserate and offer my condolences.
>
> NB/ In Windows Server 2003 you also have the option of using the /userva
> switch, rather than /3GB, that allows finer granularity of the user mode
> memory allocation.
>
> Good luck.
>
> --
> *mike hodgson*
> http://sqlnerd.blogspot.com
>
>
>
> JTT wrote:
>
>

JTT

2006-02-25, 9:27 am

Vincent-

Maybe the the other group would have been more appropriate. But since my
scenario was directly related to how to get SQL to use more memory and I
found other posts related to the switches in this same newsgroup I opted to
post here and Mike gave me the answer that confirmed what I already knew.

Thanks

JTT

"Vincent Xu [MSFT]" wrote:

> Hi JTT,
>
> Thanks Mike's excellent explanation and you may also refer to:
>
> 833721 Available switch options for the Windows XP and the Windows Server
> 2003 Boot.ini files
> http://support.microsoft.com/defaul...kb;EN-US;833721
>
> Actually I think this problem is foreign to SQL Server but it is related to
> Widows Server 2003. I think Windows Server 2003 Newsgroup would be a more
> approprate place for such issue.
>
> Have a good day~
>
> Best regards,
>
> Vincent Xu
> Microsoft Online Partner Support
>
> Get Secure! - www.microsoft.com/security
>
> When responding to posts, please "Reply to Group" via your newsreader so
> that others may learn and benefit from your issue.
>
> This posting is provided "AS IS" with no warranties, and confers no rights.
>
>
> --------------------
> are
> with
> them
> the
> your
> like
> standard
> order
>
>

Ajuss

2006-02-25, 9:27 am

Hi,

In this Article

http://support.microsoft.com/defaul...0&Product=sql2k
it says
Use of the /PAE switch in the Boot.ini and the AWE enable option in SQL
Server allows SQL Server 2000 to utilize more than 4 GB memory. Without the
/PAE switch SQL Server can only utilize up to 3 GB of memory.

So if AWE is enabled on a 6GB machine (boot.ini as /PAE )with 5G given as
max mem for SQL ,do we still need to give /3gb switch ?

Please clarify
Thanks
Ajuss
"JTT" wrote:
[color=darkred]
> Vincent-
>
> Maybe the the other group would have been more appropriate. But since my
> scenario was directly related to how to get SQL to use more memory and I
> found other posts related to the switches in this same newsgroup I opted to
> post here and Mike gave me the answer that confirmed what I already knew.
>
> Thanks
>
> JTT
>
> "Vincent Xu [MSFT]" wrote:
>

Mike Hodgson

2006-02-28, 8:23 pm

If you have 6GB of physical RAM in your box with the /PAE boot.ini
switch and AWE enabled for your SQL instance then that SQL instance can
access up to 4GB of the physical RAM in the box (2GB is reserved for
kernel mode address space). To address that extra GB to bring it up to
5GB you'll need to also specify the /3GB boot.ini switch. That will
allow SQL Server to address 3 of the first 4GB (the /3GB switch) plus
the extra 2GB between 4-6GB (the /PAE switch & 'AWE enabled'
sp_configure option). As you point out, you'll also need to specify a
'max server memory' setting (of 5120 to get 5GB) because with AWE memory
SQL Server cannot use its dynamic memory management functionality
(because the AWE memory is non-pageable and those pages are locked in
physical memory).

Hope this helps.

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

Ajuss wrote:
[color=darkred]
>Hi,
>
>In this Article
>
>http://support.microsoft.com/defaul...0&Product=sql2k
>it says
>Use of the /PAE switch in the Boot.ini and the AWE enable option in SQL
>Server allows SQL Server 2000 to utilize more than 4 GB memory. Without the
>/PAE switch SQL Server can only utilize up to 3 GB of memory.
>
>So if AWE is enabled on a 6GB machine (boot.ini as /PAE )with 5G given as
>max mem for SQL ,do we still need to give /3gb switch ?
>
>Please clarify
>Thanks
>Ajuss
>"JTT" wrote:
>
>
>

Vincent Xu [MSFT]

2006-02-28, 8:23 pm

Hi JTT,

Glad to hear this thread helps you.

I just say Windows Server 2003 newsgroup should be more approprate. Of
couse, you are welcome to SQL newsgroup.

Have a good day!

Best regards,

Vincent Xu
Microsoft Online Partner Support

Get Secure! - www.microsoft.com/security

When responding to posts, please "Reply to Group" via your newsreader so
that others may learn and benefit from your issue.

This posting is provided "AS IS" with no warranties, and confers no rights.

--------------------[color=darkred]
<v9pN2KROGHA.608@TK2MSFTNGXA01.phx.gbl>[color=darkred]
to[color=darkred]
Server[color=darkred
]
related to[color=darkred]
more[color=darkred]
so[color=darkred]
rights.[color=darkred]
the[color=darkred]
We[color=darkred]
changed[color=darkre
d]
so[color=darkred]
enables[color=darkre
d]
/pae[color=darkred]
which[color=darkred]

just[color=darkred]

Sponsored Links