drop diskgroup ... including contents clause did not work

--create a diskgroup on ASM instance and then create tbs on it
SQL> create diskgroup chhdg3 normal redundancy disk '/dev/rchhlv4','/dev/rchhlv5' attribute 'compatible.asm'='11.2.0.0.0','compatible.rdbms'='11.2.0.0.0';

Diskgroup created.

--create a tablespace on db instance using the diskgroup newly created and then quit from the SQL*PLUS
SQL> create tablespace chhts3 datafile '+chhdg3'

Tablespace created.

SQL> quit
Disconnected from Oracle Database 11g Enterprise Edition Release 11.2.0.3.0 - 64bit Production
With the Partitioning, Automatic Storage Management, OLAP, Data Mining
and Real Application Testing options

--drop the newly created diskgroup with including contents clause on ASM instance but failed due to ORA-15027