Progress Fathom Replication
User’s Guide

> ## Manually applying After Image extents

> During normal conditions, the target database is automatically updated with data from the source database. The updates are transmitted as blocks of data from the source’s AI transaction log. After a failure condition, it is possible that most recent blocks did not reach the target. For example, a TCP/IP failure could lose packets that were waiting for transmission.

> You can recover the missing data by manually applying the After Image extents that contain the data that has not already been applied to the target. However, you can only do so under the following conditions:

> - The `transition` property (under the `[server]` directive in the properties file) must be set to `manual`.

> - The agent must be in a pre-transition state.

> - The storage device that contains the source database AI extents must be accessible by the target machine. You cannot save AI extents on the same system where the source is running because the extents would not be accessible after a system crash. Network area storage (NAS) or storage area network (SAN) devices are ideal for storing AI extents.

> To apply AI extents:

> 1. Display failure recovery information using the following command:

>     DSRUTIL target_db_name -C RECOVERY Agent

> 2. Determine the AI extent number from the command output. Select the last applied AI extent or, if the last applied extent was completely processed, select the next available extent.

> The following shows an example of the relevant section of the command output:

>                                   .
>                                   .
>                                   .
>       Last AI Extent processed
>        AIMAGE BEGIN date:              Tue Jun  1 13:33:31 2004
>        AIMAGE NEW date:                Tue Jun  1 13:48:55 2004
>        After Image File Number:        3
>        File Last Opened:               Tue Jun  1 13:48:55 2004
>        Completely Applied to Target:    No

> Determine the file number of the last applied AI extent. In this example the last applied extent is `3`. Since the value after `Completely Applied to Target` is `No`, you will use `3` as the `extent_file_number` in Step 3.

> Since the value after `Completely Applied to Target` is `Yes`, you would use `4` as the `extent_file_number` in Step 3, since extent `3` is already completely applied.

> 3. Use the appropriate AI extent file number in the following command:

>     DSRUTIL target_db_name -C ApplyExtent extent_file_number

> As the command executes, it performs the following validation:

> - The extent must exist and must be valid.
> - The status of the extent must be `FULL`, `BUSY`, or `LOCKED`.
> - The AI extent file number either must be the same as the AI extent file number for the last AI block processed by the agent, or it must be the next extent file number (if the previous AI extent was completely processed).

> After you apply the AI extent, you can begin a manual transition of the target. For more information, see the "Manual transition" section.

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