Temporarily increase the size limit on the Exchange message store

A user can't log on to your standard Exchange server. Instead of spending the afternoon defragging the database to bring it below the 16GB limit, you can temporarily increase this limit by 1GB. Here's how.

It happens to the best of us. Things creep up and it gets difficult to regularly monitor the Exchange server's health. Eventually, you get a phone call from a user who claims that she can't log into your standard edition of Exchange server. After a little investigation, you find the following entry in the Exchange server's logs:

Event Type: Error
Event Source: MSExchangeIS
Event Category: General
Event ID: 1112
Description: The database "Mailbox Store (Server Name)" has reached the maximum allowed size. Attempting to unmount the database.
Event Type: Warning

In the past, this message would be the end of your day as you work to perform an offline defrag to the Exchange database to (hopefully) bring it below the 16GB limit imposed by the standard edition of Exchange. Now, however, you can temporarily increase this limit by 1GB, giving yourself enough room to mount the database and remove unneeded content. This only works for Exchange 2000 with service pack 3 installed and Exchange 2003. Further, this tip is only useful for the standard edition of Exchange since the enterprise edition does not impose this database size limit.

To temporarily increase the size of the Exchange information store database:

  1. Stop the SMTP service (this prevents new mail from being delivered while you fix your database size problem. Failure to stop SMTP could result in your database expanding beyond 17GB.)
  2. Start regedit
  3. Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\<Exchange Server Name>\Private-<hexadecimal string>
  4. Choose Edit > New > DWORD Value.
  5. Name the new value "Temporary DB Size Limit Extension" and press Enter.
  6. Double-click the new key name.
  7. Enter a value of "1" in the Value data box
  8. Click Decimal in the Base box
  9. Click OK.
  10. Close regedit.
  11. Mount the information store.
  12. Delete data you don't need, such as old mailboxes, or export a large mailbox to a PST file. Just get the store as far below 16GB as you can.
  13. Start the Exchange System Manager (you need to run online maintenance so any items you marked for deletion are actually removed from the store)
  14. Go to Exchange Server > Storage Group.
  15. Right-click the Mailbox Store option and choose Properties from the resulting shortcut menu.
  16. On the Database tab, choose Customize
  17. Specify a schedule that will force online maintenance to run immediately. Maintenance may take hours to run, so be prepared for a long day or night.
  18. When an event with ID 1121 appears in the system log, online maintenance has completed.
  19. Dismount the information store.
  20. Make sure that you have at least 18GB of disk space available.
  21. Run an offline defrag to further compress the store: exchsrvr\bin\eseutil /d "path to .edb file" /tX:\dbdefrag.edb
  22. Mount the store.
  23. Make a backup.

It's a very long process, but is much better than losing all of your mail.

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