These views provide information about the current status of locks in the database:
Lists all sessions holding locks for whose release others are waiting.
Lists all existing DDL locks.
Lists all existing DML locks.
Lists all KGL (library cache) locks in the database.
Contains internal information for each lock defined in DBA_LOCKS.
Lists all locks held or requested in the database.
Lists all sessions that are waiting on a lock held by another session.
Shows which locks the current user has allocated.