Escort Journaling

On-line Database Loading Facility

  • Description

    On-line Database Loading Facility

    Escort Journaling allows databases to be loaded on-line, while the "source" data files are being accessed and updated. This is especially important in cases where customers are upgrading from Enscribe to NonStop SQL, but have little or no downtime window for doing the actual data migration. On-line database loading using Escort Journaling eliminates costly application downtime, improving customer application availability, yet provides an efficient method for replacing database files on-line.

    Escort Journaling captures changes that occur during the on-line background database load, and then applies these changes to the new file, all on-line during normal application processing!

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  • How Does Escort Journaling Work?

    This diagram illustrates how a database file, (currently the active database) can be used as a source to load a new file and how Escort Journaling captures the changes and then applies these to the destination new data file - all as an on-line operation.

    The process should allow most applications to have minimal downtime or outage for the cut-over (i.e., a very few minutes)

    Step
    Description
    Step 1 - Application Live
    The current application is accessing the "source" file as normal.
    Step 2 - Begin Journaling
    Within Escort, start Journaling capture of changes to "source" file.
    Step 3 - Start DB Load
    Begin the background loading process. This loads the data from the "source" to the "destination" new file, in the background, while activity continues to occur by the applications to the "source" data, as Escort Journaling captures any changes in the Journal file.
    Step 4 - Apply Journal
    Once the background load of the data is complete, begin applying the Journalled database changes from the Journal file to the "destination" file. Note: Journaling is applying changes from the Journal file to the "destination" while continuing to capture new Journal changes, as the applications are still using the "source" file at this point in the process.
    Step 4a
    When the bulk of the journalled changes have been applied to the "destination" file and it is convenient to perform that actual switch over, the application programs should be briefly suspended to allow the final Journaling entries to be captured and applied to the "destination".
    Step 5 - Redirect Applications
    When the Journal file is empty (i.e., all changes to the "source" have been applied to the "destination" by Escort Journaling), the application should be changed to point to the new file (i.e., was "destination" and will now become the live database), and the application programs should be allowed to resume processing against the new database.

  • Resources

  • Related Products

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