Extracting CREATE DISKGROUP command from dictionary

Hi All, Is there a way to extract the DDL of create diskgroup command that was used earlier to create the diskgroup? I'm on AIX 7.1 and Oracle 11.2.0.3

This command fails

SQL> r
  1  select dbms_metadata.get_ddl(UPPER('&ENTER_OBJECT_TYPE'),UPPER('&ENTER_OBJECT_NAME'),
  2  UPPER('&ENTER_OBJECT_OWNER'))
  3* from dual
Enter value for enter_object_type: DISKGROUP
Enter value for enter_object_name: DGDATA1
old   1: select dbms_metadata.get_ddl(UPPER('&ENTER_OBJECT_TYPE'),UPPER('&ENTER_OBJECT_NAME'),
new   1: select dbms_metadata.get_ddl(UPPER('DISKGROUP'),UPPER('DGDATA1'),
Enter value for enter_object_owner: