Mastering Active Directory - Second Edition

Offline defragmentation

In any database system, the data will be added, modified, and deleted as it goes. When new data is added, it requires new space inside the database. When the data is removed, it releases space to the database. When the database is modified, it either needs new space or releases space. In the AD database, once an object has been deleted, it releases the space it used to the database, and not to the filesystem. Therefore, that free space will be used for new objects. This process is called online defragmentation because it does not need to stop the AD services. By default, it runs every 12 hours.

However, when a large number of objects or a global catalog server are removed, it is worth releasing this free space to the ...