ASM Administration and Management
Administering an ASM instance is similar to managing a database instance but with fewer tasks. An ASM instance does not require a database instance to be running for you to administer it. An ASM instance does not have a data dictionary, because metadata is not stored in a dictionary. ASM metadata is small and stored in the disk headers. SQL*Plus can be used to perform all ASM administration tasks in the same way you work with a normal RDBMS instance.
To administer ASM with SQL*Plus, you must set the ORACLE_SID environment variable to the ASM SID before you start SQL*Plus. The default ASM SID for a single-instance database is +ASM, and the default SID for ASM on Oracle RAC nodes is +ASMnode#. ASM instances ...