Configuring database size limits for Exchange SP2

SP2 brings the ceiling size of an Exchange database up to 75 GB for Standard Edition and a whopping 8000 GB for Enterprise Edition. But there are still configurable database size limitations that you should be aware of.

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The release of Exchange 2003 Service Pack 2 brings with it a number of important functional changes, one of the most significant being increased database size limits. SP2 brings the ceiling for the size of an Exchange database up to 75 GB for Standard Edition and a whopping 8000 GB for Enterprise Edition.

By default, however, the configurable limit for Standard Edition's database size is only raised to 18 GB when SP2 is installed. The reason for this: 16 GB was the old size limit, so adding 2 GB to that as a safety zone seems to work well without allowing excessive growth.

For instance, if someone had installed Exchange 2003's database on a partition with only 35 GB total, they wouldn't want to allow the database to grow unchecked and possibly consume the whole partition, so they would want to leave the 18 GB configurable limit in place for the time being. Later, after upgrading to a bigger server, they could then set the limit higher and not worry about running out of space.

The configurable size limits for Exchange are stored in the registry under:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\MSExchangeIS\<server_name> \Private-<GUID>

where <server_name> is the name of the Exchange server, and <GUID> (which will vary between installations) is the same as the objectGUID attribute on the database's Active Directory object entry.

The settings used are listed below. Note that if they are not present in the registry, they will need to be created.

Database Size Limit in GB (REG_DWORD): The default is 18 (even if no entry is present), but this can be set from 1-75 (decimal) in Standard Edition and from 1-8000 (decimal) in Enterprise Edition.

Database Size Buffer in Percentage (REG_DWORD): This controls the percentage margin used to log an event / warning when the database is about to reach its configured size limit. For instance, if this were set to 10 (decimal), a warning would be logged when the database was within 10% of reaching its configured size limit. The default is 10, but this can be set from 1-100 (decimal).

Database Size Check Start Time in Hours From Midnight (REG_DWORD): This controls when the database's size is checked against its configured limits. By default, this is 5 (decimal), meaning the check takes place at 5 a.m. Only one check happens every 24 hours. If the database is brought online after the check time, the check will not take place until the appointed time comes around again.

About the author: Serdar Yegulalp is editor of the Windows Power Users Newsletter.


Why wait until you get a new server? You are correct in stating that I would want to make sure the partition size is increased. But, I would just buy a new, larger drive, create a new partition and then move the database to that partition. On a current server that has no need for upgrading, this is a major benefit and easy to do. I still have users, however, who come close to the 2 GB mailbox limit.
—David R.

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