Managing the Store & DAG: EXCERPT from Microsoft® Exchange Server 2013 Inside Out

Rebuilding a database

As you know, Exchange performs ongoing online defragmentation to achieve maximum page contiguity and space usage within the database. The overall size of the database is not affected by online defragmentation because pages freed by processing are recycled and made available to the Store to hold new items. Offline defragmentation or a database rebuild is accomplished by taking the database offline and then running the ESEUTIL utility in /D mode to build a new copy of the database by reading all the pages out of the old database and writing them into the new. Depending on system performance and the size of the database, an offline rebuild can take a long time, and the only thing it accomplishes is the return of unused space ...