How can I change the store limits in Exchange 2003 SP2?

By default, the size limit of each database on a server running Exchange 2000 and Exchange Server 2003 Standard Edition is 16 GB (this limit is also enforced in SBS 2000/2003). Exchange Server 2003 Service Pack 2 (SP2) is supposed to remove this limit and thus allow for further DB size growth.

After installing Exchange Server 2003 Service Pack 2, the default size limit for each Exchange database is 18 GB, but can easily be configured to allow for database size limits of up to 75 GB per database (for the Standard and SBS 2003 versions), or up to 8000 GB (or 8 TB) per database (for the Enterprise version).

By default, Exchange 2003 SP2 logs events when the database has grown to within 10% of the configured database size limit (i.e. using 90% of the allocated limit). This threshold is configurable and can range from 1% to 100%.

BTW, you can easily check your store size by performing the steps outlined in the Reporting Storage Size in Exchange article.

The database size check happens at 5am, every 24 hours by default. This time can be changed through the registry. The first database size check will not take the database offline if the size limit has been exceeded, but an error event (ID 9689) will be logged in the Application event log (i.e. it has reached the 18 GB limit, or any other limit you have manually set).

On the second check (24 hours later) the error event will be logged in the Application event log and the database will be taken offline. An administrator can then mount the database but he or she will have 24 hours fix this issue before the database goes offline again.

Important note: Exchange 2003 SP2 now calculates the logical size of the store, and not the actual size it takes on the hard disk. For example, if you have a 30 GB store (.EDB + .STM files combined) but within it you have 5 GB of white space (look at event id 1221) then Exchange will look only at 25 GB - the logical size.

Note: Exchange 2000 Standard Edition and SBS 2000 do not have this feature and continue to have the 16 GB limit enforced.

Warning!

This document contains instructions for editing the registry. If you make any error while editing the registry, you can potentially cause Windows to fail or be unable to boot, requiring you to reinstall Windows. Edit the registry at your own risk. Always back up the registry before making any changes. If you do not feel comfortable editing the registry, do not attempt these instructions. Instead, seek the help of a trained computer specialist.

To configure the database size limit for a database:

1. On the computer running Exchange Server, start Regedit.exe.

2. Open one of the following registry keys:

• To configure the database size limit on a mailbox store, use the following registry key:

HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\Server name\Private-Mailbox Store GUID

• To configure the database size limit on a public store, use the following registry key:

  HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeIS\Server name\Public-Public Store GUID

Note: In some cases you might find more than one "Private-Mailbox Store GUID" and "Public-Public Store GUID" values in the above registry path. These values can be determined by looking at the objectGUID attribute of each store.

In order to view this value you should use a tool like LDP.exe or ADSIEDIT.msc (both can be found in the Windows Server 2003 Reskit Tools - Download Windows 2003 Reskit Tools).

Navigate to the following DN:

CN=Mailbox Store (servername),CN=First Storage Group,CN=InformationStore,CN=servername,CN=Servers,CN=First Administrative Group,CN=Administrative Groups,CN=Organization name,CN=Microsoft Exchange,CN=Services,CN=Configuration,DC=domain,DC=com

Note the objectGUID attribute of each store, then find the appropriate value in the registry path mentioned in step #2.

3. Create a new DWORD entry called "Database Size Limit in Gb" and give it the appropriate value for maximum database size in GB.

For Exchange Server 2003 Standard Edition type a value between 1 and 75 (the default is 18 GB).

For Exchange Server 2003 Enterprise Edition type a value between 1 and 8000 (the default is 8000 GB). Click OK.

Note: Entries should be in decimal format.

Note: The setting in Exchange Server 2003 Enterprise Edition is useful when you want to limit the store size, mostly due to hardware restrictions.

4. Create a new DWORD entry called "Database Size Buffer in Percentage" and give it the appropriate value between 1 and 100 to specify when you want events to be logged in the application log in Event Viewer to warn you that you are nearing the maximum size for a database.

The default value of 10 (i.e. 10%) will result in warning events to be logged when you have 10 percent capacity left before you reach the maximum size for that database.

5. Create a new DWORD entry called "Database Size Check Start Time in Hours From Midnight" and give it the appropriate value between 0 and 23 to specify when you want Exchange to check the database size.

The default value of 5 results in Exchange Server checking the database size 5 hours after midnight (i.e. 5:00 AM).

6. Close Registry Editor.

I'm not sure if I've mentioned this but you should dismount and mount your stores, or restart the Information Store service for this tip to work.