Sometimes you may want to run an SQL statement from within RMAN. Use RMAN's sql command to do this.
For Example :
RMAN> sql "alter system switch logfile";
If there are single quote marks in your SQL, you need to use two single quote marks as shown in this next example:
RMAN> sql "alter database datafile ''/d0101/ordadta/brdstn/users_01.dbf'' offline";
Some SQL commands, such as ALTER DATABASE, are directly supported by RMAN. These can be executed directly from the RMAN command prompt, without using the sql command.
For example:
RMAN> alter database mount;
RMAN> SHUTDOWN IMMEDIATE # closes database consistently
RMAN> STARTUP MOUNT
To change the state of a target database that is in NOMOUNT or MOUNT state, you must either use SQL*Plus or use the RMAN SQL command to issue a SQL statement, as shown in these examples:
RMAN> SQL 'ALTER DATABASE OPEN';
*********** You can also run O/S commands using a similar technique with the host command:*************
RMAN> host "ls";