Validating date in oracle
In previous releases of the Oracle database, RMAN had to examine every block in the data file to determine which blocks had been changed when performing an incremental backup.
When a backup is executed with Recovery Manager, the database blocks are read and corruption is automatically detected.In a bitmap index, a bitmap for each key value replaces a list of rowids.Each bit in the bitmap corresponds to a possible rowid, and if the bit is set, it means that the row with the corresponding rowid contains the key value.The time to perform an incremental backup is now proportional to the amount of content modified since the last backup.Here are the steps RMAN will perform to do an incremental backup: 1.It retains the change history for a maximum of eight backups.
The size of the file is calculated by the following formula: Size of the Block Change Tracking File = ( (Threads*2) number of old backups ) * database size in bytes / 250,000 The initial size for the block change tracking file is 10 MB.
This feature allows backups to be performed that contain only database blocks that have changed since the last full or incremental backup. It can also reduce the time required to do a restoration.
A typical scenario would be to perform a weekly full backup and daily incrementals.
Bitmap indexes are widely used in data warehousing environments.
The environments typically have large amounts of data and ad hoc queries, but a low level of concurrent DML transactions.
Moreover, unfortunately the change tracking file cannot be moved without shutting down the database, moving it with the appropriate ALTER DATABASE RENAME FILE command, and then restarting the database.