How to Delete ASM ?

Log in to the asm instance as Oracle User

$ export ORACLE_SID=+ASM

$ sqlplus / as sysdba

Enter the following command to determine whether any Oracle database instance is using the ASM instance: 

SQL> select instance_name from v$asm_client;

#Do not remove if any database is using this asm instance.

List all the diskgroups.

SQL> select name from v$asm_diskgroup;

NAME
------------------------------
DATA
FLASH

Drop Them.

SQL> drop diskgroup DATA including contents;

Diskgroup dropped.

SQL> drop diskgroup FLASH including contents;

Diskgroup dropped.

SQL>shutdown immediate

 
Remove the asm entry from the oratab file.