Issue: Your Exchange 2007 database is dismounted, according to the application event logs the database size has exceeded 250 GB
Exchange store ‘First Storage Group\Mailbox Database’: The logical size of this database (the logical size equals the physical size of the .edb file minus the logical free space) is 250 GB. This database size has exceeded the size limit of 250 GB.
This database will be dismounted immediately.
Resolution: There are two ways to resolve this issue, increasing the size limit by editing the registry and creating additional databases to distribute your data more evenly. I recommend both courses of action.
Note: Running an offline defrag using ESEUTIL will not help resolve the DB Size Limit issue because Exchange is looking at the logical space used not the physical size of the database on disk.
Solution 1 – Increase the Exchange 2007 Database Size Limit:
Open Regedit and browse to the following registry key: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\[SERVER NAME]\Private-[database GUID]
You can find the GUID of a database by running the following command in the Exchange Management Shell:
Get-MailboxDatabase -Identity “<server name>\<storage group name>\<database name>” | Format-Table Name, GUID
If the key “Database Size Limit in GB” DWORD already exists under the subkey “Private-[database GUID]”, change its value to the desired size in gigabytes, be sure to select ‘decimal’ when you enter the number.
If the “Database Size Limit in GB” DWORD does not exist for the subkey then create a new DWORD “Database Size Limit in GB”, and then set its decimal value to the desired size in gigabytes.
Note: You may need to restart the information store service for the changes to take effect.
Long term recommendations – distribute data across new databases:
I recommend you create additional mailbox databases in order to distribute your load. On Exchange 2007 I try to keep my databases below 100GB so keep that in mind when you forecast how many databases you will be creating. Remember Exchange 2007 Standard Edition only allows 5 databases including the Public Folder Database. It is also recommended to create a new Storage Group for each database. Once your new databases are creating you can use the move-mailbox command to move mailboxes into the new databases.
Note: The size on disk of your existing database that you are moving mailboxes out of will not decrease however the logical size has decreased and that’s what Exchange looks at for it’s size limitations.