How add or alter ASM DG in RAC

1. Dismount the diskgroup in one node

17:11:52 SYS@+ASM2 SQL> alter diskgroup tba1 dismount;

Diskgroup altered.

2. Drop it from the other instance where it is mouted

17:09:32 SYS@+ASM1 SQL> drop diskgroup tba1 ;

Diskgroup dropped.

3. Use that disk in any of the existing diskgroup or add a new group.

17:12:02 SYS@+ASM2 SQL> alter diskgroup sys2 add disk '/dev/rdsk/emcpower15a' rebalance power 3;

Diskgroup altered.