If a PowerExchange Express capture process stops and is then warm started, PowerExchange Express CDC uses the checkpoint information to resume the processing of outstanding transactions from the last recorded checkpoint. By using a checkpoint, Express CDC avoids time-consuming reprocessing of large amounts of redo log to rebuild the state of all transactions that were active when the process stopped.

You can store state information for in-flight transactions in file-system files or in three Oracle tables. For file-based storage, ensure that the user ID under which Express CDC runs is granted the appropriate permissions to create the files. For table-based storage, ensure that the database user has the appropriate permissions to create and update the tables. You can manually create the tables or allow Express CDC to automatically create them. The first initialization of a CDC process after checkpointing is enabled causes Express CDC to automatically create the tables if they do not already exist. If you need to manually create the tables, use the DDL statements that are documented in the

PowerExchange CDC Guide for Linux, UNIX, and Windows

to ensure the schema is correct.

To configure checkpointing, you must specify the CHECKPOINT statement and STATESTORAGE statement in the PowerExchange Express CDC configuration file. Optionally, if you want to encrypt the spill files that contain checkpointed data, you can optionally set the SPILLENCRYPTPASS or SPILLENCRYPTEPASS parameter in the OPTIONS statement.

For more information, see the "Express CDC for Oracle" chapter in the

PowerExchange CDC Guide for Linux, UNIX, and Windows

.