Accelerated Oracle Incremental Backup with change tracking technology

Oracle 8i introduced recovery management (RMAN), and for the first time true incremental backups were implemented. The database output can also be incremented before Rman, but the entire table needs to be overridden once any piece of a table has changed. An Rman incremental backup only needs to overwrite the modified part in a given data file, thus greatly saving space.

However, before version 10g, incremental backups require a scan of the entire data file to determine which blocks of data have changed. For large databases, although space is saved, its time complexity is no better than a full backup.

The change tracking technique (sometimes called block Change tracking technology) solves the problem by recording the changed blocks in a separate trace file, which is written to the file in real time by a background process.

The initial incremental backup still requires a full scan. After that, you can access the blocks that need to be backed up directly by changing the trace file by reference.

To create and activate a change tracking file, first make sure that the database is open or accessible, and then run the following database change (ALTER DATABASE) command:

ALTER DATABASE
ENABLE Block Change Tracking
USING FILE <pathname>;

To change the location where the trace files are stored in the operating system. (If you activate the Oracle management file, the using clause is optional and the change tracking file will be created in the Db_create_file_dest directory.) ）

Regardless of where the path of the file is located, its initial size is 10MB, and each increment of 10MB is required.

Using the change tracking technique will affect system performance, so unless you need to use the Rman incremental backup feature, you might want to make it unavailable.