ExMerge Strategies and Best Practices


Typically, ExMerge can extract one gigabyte of mailbox data per hour. To merge all data from a large database can take several hours to several days. By using multiple copies of ExMerge or by filtering data, you can restore the most critical data first. ExMerge can detect duplicate items, and it will not insert multiple copies of a single message even if run in multiple passes. Suggested practices include:

  • Learn how to use ExMerge before you need it.

    You should thoroughly understand the filtering capabilities in the Options menus. The Mailbox Merge documentation is comprehensive and describes capabilities that may be useful to you for purposes other than disaster recovery.

  • Run multiple copies of ExMerge simultaneously.

    Typically, running three or four ExMerge processes at once produces the highest data extraction rates. If possible, run each ExMerge process from a separate computer. If you are running several copies of ExMerge from the same computer, make separate copies in separate folders of the ExMerge.exe and ExMerge.ini files, and start each instance of ExMerge from a separate default folder. This approach provides the greatest flexibility and prevents the ExMerge log files from interfering with each other.

  • Filter the folders extracted by ExMerge so that the most important folders are restored first.

    For example, during the first ExMerge run, select "Ignore these folders" and filter Sent Items and Deleted Items. These two folders often are the largest in a mailbox, but they are the least frequently accessed. Next, set a "Process only these folders" filter that includes Sent Items and Deleted Items. Finish restoring all mailbox data with a second run of ExMerge.

  • Restore high-priority mailboxes first or in a parallel, dedicated ExMerge process.

    Before you need it, make a list of personnel whose core job functions depend most heavily on access to Exchange data (for example, executives, executive assistants, and sales personnel).

  • When possible, merge data from a smaller database to a larger database, rather than vice versa.

    This approach can dramatically reduce your total recovery time. For more information about this approach, see Recovering a Mailbox Database Using a Dial Tone Database in Exchange Server 2003.

  • Use ExMerge to make "brick" or single mailbox backups of the most critical data for your most important users.

    You can script ExMerge to make regular incremental backups of data to individual .pst files that can be distributed to end users in an emergency.

  • If you encounter failures, use the –logmax command line switch or set LoggingLevel = 3 in the ExMerge.ini file to assist in troubleshooting.

  • If you encounter a failure with one database or mailbox, try a mailbox in another database or even a mailbox on a different server to help determine the scope of a problem.

    If the problem occurs with mailboxes not in the recovery storage group, you can troubleshoot the failure as a generic ExMerge issue rather than a recovery storage group issue.

  • If you are implementing the Messaging Dial Tone strategy and swapping databases as described in Recovering a Mailbox Database Using a Dial Tone Database in Exchange Server 2003, do not merge rules, permissions, or associated folder data.

    Be aware that until the swapping and merging processes are complete, some rules may no longer be effective, especially rules that move messages to user-created folders. User-created folders have unique folder IDs (FIDs) that rules depend on. A folder of the same name created in a different database (such as the dial tone database) has a different FID, and to point to the new folder, you must edit the rule or an error will occur. Then, once the recovery process is complete, the original folders return to their places, and you must edit the rule a second time to work correctly.