Microsoft added functionality in the Exchange 2000 Server post-Service Pack 3 (SP3) rollup to enable an extra 1GB of database growth for a standard edition database. You can use this extra space to perform maintenance in emergency situations when you run out of database space. This capability is standard with Exchange Server 2003. To access this additional storage, perform these steps:
1. Start the registry editor (regedit.exe) on the Exchange server.
2. Move to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesMSExchangeISSAVDALDC01Private-
3. From the Edit menu select New – DWORD value.
4. Enter a name of Temporary DB Size Limit Extension and press enter.
5. Double-click the new value and set it to a value of 1. Click OK.
6. Close the registry editor. You should immediately perform the database maintenance to reduce its size, then delete the temporary size limit extension value.
As the name suggests, this extra space is temporary, and if you use up this 1GB you have no options left (except upgrade to Exchange 2003 SP2 or buy Exchange 2003 Enterprise Edition). You need to dismount and mount the Store for the change to take effect.