Introduction to Administering the Active Directory Database

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Active Directory is stored in the Ntds.dit database file. In addition to this file, the directory uses log files, which store transactions prior to committing them to the database file. For best performance, store the log files and the database on separate hard drives.

The Active Directory database is a self-maintained system and requires no daily maintenance, other than regular backup, during ordinary operation. However, it may need to be managed if the following conditions occur:

  • Low disk space

  • Pending or current hardware failure

  • A need to recover physical space following bulk deletion or removal of the global catalog

Monitor free disk space on the partition or partitions that store the directory database and logs. The following are the recommended parameters for free space:

  • Ntds.dit partition: The greater of 20 percent of the Ntds.dit file size or 500 megabytes (MB).

  • Log file partition: The greater of 20 percent of the combined log files size or 500 MB.

  • Ntds.dit and logs on the same volume: The greater of 1 gigabyte (GB) or 20 percent of the combined Ntds.dit and log files sizes.

During ordinary operation, the customer will delete objects from Active Directory. When an object is deleted, it results in white space (or unused space) being created in the database. On a regular basis, the database will consolidate this white space through a process called defragmentation, and this white space will be reused when new objects are added (without adding any size to the file itself). This automatic online defragmentation redistributes and retains white space for use by the database, but does not release it to the file system. Therefore, the database size does not shrink, even though objects might be deleted. In cases where the data is decreased significantly, such as when the global catalog is removed from a domain controller, white space is not automatically returned to the file system. Although this condition does not affect database operation, it does result in large amounts of white space in the database. You can use offline defragmentation to decrease the size of the database file by returning white space from the database file to the file system.

Managing the Active Directory database also allows you to upgrade or replace the disk on which the database or log files are stored or to move the files to a different location, either permanently or temporarily.

Prior to performing any procedures that affect the directory database, be sure that you have a current system state backup. For information about performing system state backup, see Back up system state.

To manage the database file itself, you must take the domain controller offline by restarting in Directory Services Restore Mode, and then use Ntdsutil.exe to manage the file.


NTFS disk compression is not supported for the database and log files.