1. Block Change Tracking: Oracle RMAN’s Block Change Tracking (BCT) feature helps speed up incremental backups by tracking blocks that have changed since the last backup. This makes it possible to skip scanning blocks that haven’t changed, reducing the time required to complete the backup. When enabled, the database writes a file to disk that contains information about the changed blocks, which RMAN uses during the incremental backup process.
Enabling BCT is straightforward - simply set the parameter ‘DB_CREATE_FILE_DEST‘ to a directory where the tracking file can be written. Then, set the parameter ‘CHANGE_TRACKING‘ to ‘ON‘ for each datafile that you want to track changes for. For example:
ALTER DATABASE ENABLE BLOCK CHANGE TRACKING USING FILE '<path_to_tracking_file>';
ALTER DATABASE DATAFILE '<datafile>' ENABLE BLOCK CHANGE TRACKING;Enabling BCT can improve backup performance significantly, especially for large databases with high rates of change. However, it does require some extra disk space to store the tracking file, and it may impact overall database performance since it adds some overhead to the block modification process.
2. Tablespace Point-in-Time Recovery (TSPITR): Oracle RMAN’s Tablespace Point-in-Time Recovery (TSPITR) feature allows you to recover one or more tablespaces to a point in time before a problem occurred. This can be useful if you have a damaged tablespace or if you accidentally dropped a table or schema.
To perform a TSPITR, you need a backup of the affected tablespaces, as well as archived redo logs that cover the desired recovery time period. You’ll also need to create a recovery catalog, if you haven’t already done so.
The basic steps to perform a TSPITR are:
- Use RMAN to restore the backup of the affected tablespaces to a separate location.
- Recover the restored database to the desired point in time using the archived redo logs.
- Export the recovered tables or tablespaces using Oracle Data Pump or other export tool.
- Import the exported data into the target database.
TSPITR can be a powerful tool for recovering from certain types of data loss scenarios. However, it does require some extra steps and can be time-consuming, particularly if you have a large database or if you need to recover multiple tablespaces.
3. Incrementally Updated Backups: Oracle RMAN’s Incrementally Updated Backups feature allows you to create an incremental backup that includes only the changed blocks since the last backup, then merge that backup into a full backup. This can help reduce backup windows and storage requirements, as well as provide faster recovery times.
To perform an Incrementally Updated Backup, you’ll need to have a Level 0 backup of the database, as well as one or more Level 1 backups that were created using the ‘BACKUP INCREMENTAL LEVEL 1 CUMULATIVE‘ command. The basic steps to create an Incrementally Updated Backup are:
- Use RMAN to create a new Level 1 backup using the ‘BACKUP INCREMENTAL LEVEL 1 CUMULATIVE‘ command.
- Run the ‘BACKUP INCREMENTAL LEVEL 0 MERGE‘ command to merge the Level 1 backup into the existing Level 0 backup.
Incrementally Updated Backups can be a powerful tool for reducing backup windows and storage requirements, as well as for providing faster recovery times. However, they do require some extra overhead to create and maintain the incremental backups, and they may require more disk space than traditional full backups if you have a high rate of change in your database.
Overall, these advanced Oracle RMAN features can be very useful for improving backup and recovery performance, as well as for recovering from certain types of data loss scenarios. By understanding their strengths and weaknesses, you can determine which features are best suited to your specific needs and deploy them accordingly.