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DML Locks
Taken automatically when DML issued
TX – Transaction Locks
TM – DML Enqueue Locks
- Object locks, prevent altering of structure while DML active
Held until COMMIT or ROLLBACK
Notes:
DML operations that acquire locks include UPDATE, DELETE and INSERT. Oracle acquires two types of locks when a DML operation is executed, a TX lock and a TM lock. A TX lock is a transaction lock and is the row level lock that is placed on each row affected by the DML operation. A TM lock is also taken on the object affected by the DML operation and prevents the object from being altered while your transaction is active.
These locks are held until the transaction commits or rolls back.