Exchange Server 2000 Standard Edition enforces a limit on how big the message database can be. The maximum allowed size is 16 gigabytes. If you try to insert more than 16 GB of data, you run the risk of corrupting your Exchange database.
When the database approaches the 16 GB threshold, it may spontaneously dismount to prevent a problem, and Exchange will usually log an error about the database size. Consequently, if the database hits the 16 GB limit, it becomes difficult to mount the message store long enough to remove unneeded data and perform a defragmentation.
Microsoft has created a workaround for this problem, which was enabled in the September 2003 Exchange 2000 post-Service Pack 3 rollup (see Knowledge Base article 824282), and is available by default in Exchange Server 2003.
The fix allows you to temporarily increase the size of your database by 1 GB, which usually provides enough work space for you to selectively delete data and defragment the message store so the database can be shrunk safely.
To enable this, open the registry on the Exchange 2000/2003 server computer and navigate to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS
\<server_name>\Private-<hex_string>
where <server_name> is the name of the Exchange server, and <hex_string> is a long string of hexadecimal characters that will vary from computer to computer.
In this subkey, create a REG_DWORD value named Temporary DB Size Limit Extension and set it to 1. Then remount the message store and perform any needed maintenance to bring down the size of the message store.
When this feature is enabled, Event 9657 will be logged to remind you that the temporary size limit extension is enabled. Be sure to disable the extension (i.e., set the above DWORD value to 0) when you've finished maintenance on the database.
If you're constantly exceeding the 16 GB database size limit for Exchange Server 2000 Standard Edition, you may need to rethink your message retention policy or even consider moving to Exchange Server Enterprise Edition, which allows a total of 16 terabytes in the message store.
About the author: Serdar Yegulalp is editor of the Windows 2000 Power Users Newsletter and a regular contributor to SearchExchange.com.
Do you have comments on this tip? Let us know.
