The database size limit registry keys are read when the database mounts (not when the service starts) and when each limit check task runs.
You must set registry parameters for each database on the server. The registry entries are located under each database entry in the local server registry. Accordingly, you must reset the registry keys manually if the server has to be rebuilt using the /disasterecovery setup switch.
The registry setting is created in the following registry location, the GUID in this key (Private-SID) is an example and should match the value of the objectGUID attribute on the database’s AD object:
Database Size Limit in GB
The Database Size Limit in GB setting is the configurable maximum size of a database not to exceed the maximum licensed size of your database. For Standard Edition, you can set the database size limit between 1 and 75 GB. By default, the limit is 18 GB. Follow the steps below to change the maximum size of the database:
1. Launch regedit by going Start > Run and entering regedit then hitting Enter.
2. Browse to the following folder:
3. Right click in the right hand pane and select New > DWORD Value.
4. Enter “Database Size Limit in GB” without the quotes for the name.
Note: The registry value mentioned is a decimal, not a hexadecimal.
Behavior When the Database Size Limit is Reached
The database size is calculated at 5:00 AM server time daily. This check is done against the physical database file size, if this file size is over 90% of the total database size limit, then the check will calculate free space in the file and subtracts that from the total file size.
When the database size is 90% of the Database size set in the registry key above, an error event (ID 9688) is logged in the Application event log.
With Exchange Server 2003 SP2 or later, the server performs the following tasks when the database size limit is reached:
* If the first check after a database mount finds the database size above the limit, the database will not be taken offline but an error event (ID 9689) will be logged in the Application event log.
* If it is the second check, an error event (ID 9689) will be logged in the Application event log and the database will be taken offline.
After the database has been remounted, the administrator has until the next database size check, 5:00 AM server time, to take corrective action.