[Backup and recovery] restore data files in archivelog Mode

Cause:

For non-important files, it usually does not cause the instance to crash. Oracle will take these damaged data files offline and make their content inaccessible, but the rest of the database should be open.

Damaged important data files can cause database crashes. When you try to start the service, the database will stay in the loading mode, and an error message indicating the impaired range will be written in the alarm log.

Solution:
Method 1 (non-important files are damaged ):
When RMAN is used to back up the corresponding Tablespace.
RMAN> SQL "alter tablespace <tablespace name> offline ";
RMAN> run {
2> resotre datafile <datafile number>;
3> recover datafile <datafile number>;
4>}
RMAN> SQL "alter tablespace <tablespace name> online ";
Method 2 (important files are damaged ):
The recovery steps for damaged important data files are the same as those for non-important files. However, database crashes due to damage to important data files. It can only be started to the loading mode. Important data files should be restored and restored in the loading mode. In addition, Offline and Online operations on Tablespace are not required.

Note:
Damage to important data files does not mean data loss, but time loss.