AT AN OPERATING SYSTEM PROMPT, SET YOUR ORACLE_SID ENVIRONMENT VARIABLE TO THE NAME OF THE ASM INSTANCE, AND LAUNCH THE ASMCMD UTILITY
1. At an operating system prompt, set your ORACLE_SID environment variable to the name of the ASM instance, and launch the ASMCMD utility. On Windows:
set ORACLE_SID=+asm
asmcmd.bat
Or on Unix:export ORACLE_SID=+asm
asmcmd