HOW TO CREATE RMAN RECOVERY CATALOG DATABSE

The catalog database is usually a small database it contains and maintains the metadata of all rman backups performed using the catalog.
Use multiple database with same recovery catalog

/////////Create database using DBCA for recovery catalog with name as example rman....

/////Create tablespace for recovery catalog 

SQL>  create tablespace rman_catalog

           datafile '/opt/oracle/oradata/rman/rman01.dbf'

           size 10M autoextend on

           extent management local uniform size 1M

////Create user to maintain recovery catalog

 SQL> create user rman identified by rman

            default tablespace rman_catalog

            quota unlimited on rman_catalog;

///To give roles,privilige to rman user.

SQL>grant connect, resource,recovery_catalog_owner to rman;

///Connect with target database and recovery catalog 

Target database=orcl

Recovery Catalog database=rman

$ rman target sys/orcl@orcl catalog rman/rman@rman

RMAN> create catalog tablespace rman_catalog;

////Register the database to use with recovery catalog

RMAN> register database;

Verify and check using rman command 

RMAN> report schema;

report schema,list backup  etc........... on rman prompt.

Another way on recovery catalog database 

$ export ORACLE_SID=rman

SQL>conn rman/rman

SQL> select * from rc_database;

Here show database information target database with dbid