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Lesson 5 Using RMAN to resynchronize a database
Objective Demonstrate how to resynchronize a target database using the resynch command.

Using RMAN to resynchronize a Database

The recovery catalog is used to keep track of your target database and all the files required to recover your database in the event of a failure. Events relating to your target database do not automatically update the recovery catalog. These events include:
  1. Adding or dropping a tablespace
  2. Adding data files to an existing tablespace
  3. Adding or dropping rollback segments
  4. Log switches
  5. Mounting a backup or noncurrent control file
Several actions can alter the physical makeup of your target database that will not be reflected in your recovery catalog. It is important that these changes be recorded so that your recovery catalog correctly reflects the state of your target database, so it is good practice to resynchronize your database with its entries in the recovery catalog after these events.
You may run into a situation where your rollback segments sit on a corrupt disk. You could drop the existing rollback segments and add new ones. The result of these actions will not appear in your recovery catalog. You would need to force a resynchronization to update the recovery catalog. When you perform a resynchronization operation, Recovery Manager will update only those entries in the recovery catalog that are different than the control file information.

Resynch command syntax

The following is the command syntax for a resynch:
resynch catalog [from controlfilecopy < control file> ]

To resynchronize using the current control file:
RMAN> resynch catalog

To resynchronize specifying a specific control file:
RMAN> resynch catalog from controlfilecopy 


The recovery catalog is not automatically updated when a log switch occurs, when a log file is archived, or when you modify your database structure. This information is stored in the control file and should be updated to your recovery catalog.
In the next lesson, you will learn more about situations where the resynch command is used.