What is the difference between Oracle RMAN catalog and Nocatalog

Nocatalog way: With control file as a catalog, every backup to the controlling files to write a lot of backup information, control files will have more and more backup information, that is, Rman backup information written in the local control file inside.

Catalog way: You must first create a directory backup database (catalog, also known as the Knowledge Base), set up a recovery directory, that is, the database backup information written to the recovery directory.

When the Oracle database is backed up through an Rman nocatalog, Oracle uses Controlfile to store the Rman backup information. Therefore, when backing up a database using the Rman Nocatalog method, be sure to back up the controlfile.

Initialization parameter Control_file__record_keep_time set up the backup information to save the time, automatically clears the previous backup information at the specified time:

Sql> alter SYSEM set control_file_record_keep_time=7 scope=spfile;

Attention:

When using Rman nocatalog recovery, the database is at least in the Mount state, that is, the control file must be loaded first, or the Rman cannot find the backup information for the record. The prerequisite for Oracle startup mount is that control must exist. Therefore, you must restore the controlfile before restoring datafile. When you use the Rman catalog method, you can startup Nomount and then restore Controlfile, but you must first restore Controlfile in a file when you use Rman nocatalog.

The following is a comparison of the procedures for the recovery of Rman Nocatalog and Rman catalog to establish the correct backup strategy (the following recovery is a backup in online state):

Rman Nocatalog Recovery:

1 Establish an Oracle operating environment (including init or SP files)

2 file mode restore Controlfile to the location specified by the Init file (or start to Nomount first, restore Controlfile from Autobackup in Rman)

3) Startup Mount

4) Rman,restore Datafile,recover datafile

5 ALTER DATABASE Open Resetlogs

Rman Catalog Recovery:

1 Establish an Oracle operating environment (including init or SP files)

2 Rman, restore Controfile

3 ALTER DATABASE Mount

4) Rman, restore Datafile,recover datafile

5 ALTER DATABASE Open Resetlogs

As you can see, Rman nocatalog Backup, the Controlfile must be backed up in a file format.

In addition, the Control_file_record_keep_time value in the ORACLE parameter file (the default is 7 days) is recommended to be increased because the controlfile is used to store the backup information during Nocatalog, which is in the $oracle_home/dbs /initsid.ora (9i may also be in spfile and can only be changed through Oracle statements).

The recovery directory (that is, the catalog method) supports the following commands

{create| upgrade| DROP} CATALOG

{create| delete| replace| PRINT} SCRIPT.

LIST incarnation

REGISTER DATABASE

The In time

RESET DATABASE

RESYNC CATALOG

1, Resync command

Resync can synchronize the information between the database and the recovery directory, and in practice, Rman can generally synchronize automatically.

Synchronization is required in the following situations

• Changes in the physical structure of the database

• Increase or change the size of the data file

• Table Space Deletion

• Rollback segment Creation and deletion

• 10 archived logs per generation

2. Reset Order

After the target database resetlogs, the recovery directory needs to be reset. Reset command is used to reset the recovery directory.