Active Directory is a non-relational database and its size increasing over time, the database takes more and more disk space. If you remove the objects from Active Directory, the size of database file will not be changed, but the free space (white space) can be used to store new objects in that case. As any other database, Active Directory database must be periodically maintain to reduce data fragmentation, speed up search and increase LDAP-query performance.
There are two types of Active Directory database defragmentation :
- Online defragmentation – performed automatically every 12 hours. In this case, Active Directory service on a domain controller continues to work. The data in file is reorganized, free blocks are released, but the file size is not reduced.
- Offline defragmentation – performed only manually by Active Directory Administrator, but ADDS service on a DC is not available at this time. This type of defragmentation can significantly reduce AD database file size and slightly increase AD query performance.