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Where is Outlook Looking ?

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  • Where is Outlook Looking ?

    The Exchange store can be divided into two categories - Messages and Transactions. Messages are stored in the database which can be periodically updated from the transaction logs. Transactions such as writing a new message are stored in the transaction logs. Does this mean that the Outlook client is looking at BOTH the message store (made up of edb and stm files) AND the transaction logs in order to give the user a current picture. Or does Outlook simply receive information from Exchange in order to build the Outlook picture.

    May be a question for Daniel this one ?


  • #2
    Re: Where is Outlook Looking ?

    AFAIK the transaction logs are simply a backup to the message store and Outlook looks only to the store(s) for its information
    Tom Jones
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    • #3
      Re: Where is Outlook Looking ?

      The only thing that looks at transaction logs is Exchange. Outlook doesn't use them at all. That would be very inefficient as the client would have to look through all the logs to find what it needs.

      Simon Butler
      Exchange MVP

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      • #4
        Re: Where is Outlook Looking ?

        I am not sure that either of you are giving the full picture here. Exchange basically works like this:
        New message arrives and is placed in the E0x.log file. That is always the current log and is copied to the next serial number whenever it hits 5 Mb.
        When the server has some idle time, those transaction logs get played into the database, which is made up of the priv(x+1).edb and priv(x+1).stm files for the private store and similarly for the public store.
        As long as circular logging is turned off, the number of 5Mb transaction files keeps growing until an Exchange aware backup is made. At this point, after the .edb/.stm files have been backed up successfully, the fully committed log files get truncated/deleted since we have all the committed info on disk in the databases and again in the backup. IE if we restore, we only need the log files which have info that was not committed to the database at the time of the backup -all others are redundant and are therefore deleted.
        Now, what Outlook sees of all this is a bit mysterious, but it presumably can see the databses AND the log files to get the complete picture.
        So I was taught. for example.

        Steven Teiger [SBS-MVP(2003-2009)]
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        • #5
          Re: Where is Outlook Looking ?

          I'm going completely by ear here, and I haven't read the link; but I would expect Outlook to be notified by Exchange when there is a message to be read, rather than going out and looking for it. For appointments etc then of course Outlook needs to see at least the Database; but for incoming events such as emails it wouldn't need to see the database, it would simply need to be told...

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