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Online and Offline Defragmentation – What it does ??

Online defragmentation is an automated defragmentation process as a part of its scheduled maintenance which we specify on a mailbox store level in ESM where the actual database size remains the same wherein Offline defragmentation is the process we use to shrink the database size removing white spaces using the eseutil /d switch.

Things to remember about online maintenance.

Online deframentation:
Does not reduce the physical size of the database
Online defragmentation runs for 15 minutes at the end of the database maintenance cycle (assuming that a task has completed).
By default, maintenance runs from midnight to 4 a.m.
There are 11 task that is perfromed by online maintenance along with the defragmentation.  They are

1.      Purge the indexes on the mailbox and public folder stores.
2.      Perform tombstone maintenance on mailboxes and public folders.
3.      Remove expired messages from the dumpster for the mailbox and public folder stores.
4.      Remove expired messages from public folders.
5.      Remove deleted public folders with tombstones over 180 days old.
6.      Clean up message conflicts within public folders.
7.      Update server version information on public folders.
8.      Check for and remove duplicate site folders on public folder stores.
9.      Clean up deleted mailboxes on mailbox stores.
10.  Check the message table for orphaned messages (messages with a reference count of 0).
11.  Perform an online defragmentation of the store.

Offline Defragmentation
Reduces the physical size of the database
When you run eseutil /d against a database to defragment it, the streaming file associated with the database is automatically defragmented. If you do not want the streaming file to be defragmented, include the /i option.
Time that the defragmentation will take will depend on the amount of white space in the database, as well as the size of the transactions recorded in the database, and your hardware specifications.

6 Responses to “Online and Offline Defragmentation – What it does ??”

  1. Tania Says:

    Not sure that this is true:), but thanks for a post.

  2. Jenny Says:

    Pretty cool post. I just came across your blog and wanted to say
    that I’ve really liked reading your posts. Any way
    I’ll be subscribing to your blog and I hope you post again soon!

  3. Geek Says:

    More information on online defragmentation required Ratish…

  4. Kumar Says:

    Tania and Jenny,
    Thanks for the comment and this sounds encouraging.

    Thanks for the feedback. But could you please let us know what kind of information you expect?

    Thanks all again

  5. Muhammad Irfan Sadiq Says:

    Nice Post RAtish, i have seen lots of Exchange Admins being confused by thinking that Online Defrag is all they need to keep Exchange database Clean and healthy. I would recommend to perform Database Integrity check at least once every month in order to minimize any sort of corruption in database.

  6. Shakti Kumar Says:

    Awsome link

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