MySQL CDC Connector > MySQL CDC administration > Recovery and restart processing

Recovery and restart processing

Each type of CDC Connector supports recovery and restart processing. If a mapping task job fails or is stopped before the end of log, the Data Integration service in conjunction with the CDC client can use recovery information that is stored on the target system to resume the extraction of change records in the PowerExchange Logger log files from the point of interruption. This functionality prevents change data loss and inconsistencies between the source and target.
To enable recovery and restart processing, you must set the Recovery Strategy advanced session property to Resume from last checkpoint on the Schedule page when you create or edit a mapping task. With this recovery strategy, the Data Integration service provides for the recovery of target tables, and the CDC client and PowerExchange provide for the recovery of the CDC restart information that is used to resume extraction processing in the log files.
CDC restart information consists of PowerExchange-generated restart tokens from the source system. For a relational target, the Data Integration service stores CDC restart information in the PM_REC_STATE recovery table in the target database. Data Integration in conjunction with the CDC client automatically creates this PM_REC_STATE table on the target.
For databases where the recovery tables are not automatically created, use the template script for creating the recovery tables:
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 in the change stream 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 that extraction processing starts 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:
Note: Restart information is associated with a mapping task and 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 CDC Runtime page for the mapping task, open the Select Restart Point dialog box, and click OK. If you do not take one of these actions, the mapping task will fail the next time you run it.