The built-in reports Locks by User and Blocking Locks by User (found in Data Dictionary Reports/Database Administration/Locks) does not works in Database 12cR1 with a user having SELECT ANY DICTIONARY privilege. Also a user having DBA role is not enough in 12cR1. In 11gR2, having SELECT ANY DICTIONARY is enough.
Error displayed: ORA-01031: insufficient privileges
This might be caused by direct referencing of sys.user$ internal object in the view's definition.
Software versions used:
SQL Developer version: 188.8.131.52.29
Oracle JDK: 1.8.0_31, 64bit, Linux
Instant client: x64-184.108.40.206.0
DBMS: Oracle Database 12c Enterprise Edition Release 220.127.116.11.0 - 64bit Production, non-CDB configuration