While dismounting a diskgroup, got the below error:


SQL> alter diskgroup NEWTST dismount;
alter diskgroup NEWTST dismount
ERROR at line 1:
ORA-15032: not all alterations performed
ORA-15027: active use of diskgroup “NEWTST” precludes its dismount



There might be some running databases using that diskgroup.

check v$asm_client,for active connections to that diskgroup

The database TESTDB2 is running and using this diskgroup, shutdown the database and try to dismount.