Starting with Oracle Grid Infrastructure 11g Release 2, Oracle ASM is installed as part of an Oracle Grid Infrastructure installation, with Oracle Clusterware.
You can no longer use Database Configuration Assistant (DBCA) to perform administrative tasks on Oracle ASM.
See Also:
Oracle Automatic Storage Management Administrator's Guide for details on configuring disk group compatibility for databases using Oracle Database 11g Release 2 with Oracle Grid Infrastructure 12c Release 1 (12.1)