The Recovery Catalog consists of a set of Oracle tables and views, which are used by Recovery Manager to manage the backup, restore, and recovery of Oracle databases. The logon credentials for the Recovery Catalog database consist of a user name, a password, and optionally a service name (TNS alias) which together make up the database connect string.
A , also known as , is used to indicate what database to use. Oracle translates the service name to a connect descriptor through the tnsnames.ora file. If this field is left blank, RMAN will not use a network listener to connect to the database. In this case the selected Oracle SID determines what database to connect to. Note that, if you are using a Recovery Catalog and thereby multiple SIDs, you will want to use a service name for either the target database or the recovery catalog database because only one Oracle SID can be specified at any one time in the environment.