When you run a mapping task to capture changed data from a CDC source and write the changed data to an Amazon Redshift target table, Amazon Redshift V2 Connector supports recovery and restart processing. You cannot use recovery and restart processing when you run an elastic mapping.
If a mapping task fails or is stopped before completing the task, the Secure Agent uses the recovery information stored in the
table on the target system to resume the extraction of changed data from the point of interruption. This functionality prevents changed data loss and inconsistencies between the source and target.
To enable recovery and restart processing, set the
advanced session property to
Resume from last checkpoint
page when you create or edit a mapping task. With this setting, the mapping task can resume processing changed data from the point of interruption.
In special situations, you can specify a restart point for a mapping task. Typically, the first time you start a mapping task, you specify a restart point that corresponds to the target materialization time so that no change records are skipped. The default restart point is the end of log (EOL), which is the current point of CDC processing in the log. You can specify a restart point that corresponds to the extraction processing starting from the earliest available record in the log or from a specific date and time. When you use a time-based restart point, extraction processing starts in the log that contains the first unit-of-work (UOW) that has an end time later than the restart time.
When you specify a restart point, consider the following points:
The restart point applies to all sources in the mapping that is associated with the mapping task.
If you set a restart point that is too early, it might correspond to a expired log file. In this case, the value of the restart point is considered as the earliest available record in the available log files.
If you set a restart point that is later than the latest record in the log files, an error message is issued.
Restart information is associated with a mapping task, a specific source and target combination. If you change the source object in a mapping, you must either create a new mapping task for the mapping or increment the restart revision number for the existing mapping task. To increment the restart revision number, navigate to the
page for the mapping task, open the
Select Restart Point
dialog box, and click
. If you do not take one of these actions, the mapping task will fail the next time you run it.