A recovery catalog is not necessary when using RMAN. To use a recovery catalog, you need to create a schema in a recovery catalog database. The catalog will be located in the default tablespace of the scheme. Note that SYS cannot be the owner of the catalog.
Create the recovery catalog schema in a different host, on different disks, and in a different database from the target database you will be backing up. If you do not, then the benefits of using a recovery catalog are lost if you lose the database and need to restore.
Ensure that the recovery catalog and target databases do not reside on the same disks. If they do and you lose one database, you will probably lose the other.
The basic procedure for setting up a recovery catalog:
Create the user who will own the recovery catalog schema in the recovery catalog database. For example, start SQL*Plus and run:
-- Connect as SYS to recovery catalog database
CONNECT sys/sys@sridevi AS SYSDBA
-- Create user that will own catalog tables
CREATE USER rman IDENTIFIED by rman
TEMRORARY TABLESPACE temp
DEFAULT TABLESPACE tools QUOTA UNLIMITED ON tools;
Grant the recovery catalog owner privilege and any other desired privileges. For example, in SQL*Plus run:
GRANT RECOVERY_CATALOG_OWNER TO rman;
GRANT CONNECT, RESOURCE TO rman;
Start RMAN and create the recovery catalog schema itself with the CREATE CATALOG command. For example:
% rman TARGET / CATALOG rman/rman@catdb
RMAN> CREATE CATALOG
Register the target databases in the recovery catalog with the REGISTER DATABASE command. For example:
RMAN> REGISTER DATABASE;