1Z0-062 Question #200: Real Exam Question with Answer & Explanation

The correct answer is B: Row-exclusive lock on the row being updated. In Oracle, a DML operation such as UPDATE acquires a row-level exclusive lock on the specific row being modified, not the entire table.

Question

The HR user updates the salary of one of the employees in the EMPLOYEES table, but does not commit the transaction. Which type of lock would this scenario lead to?

Options

AExclusive table-level lock on the EMPLOYEES table
BRow-exclusive lock on the row being updated
CNull lock on the EMPLOYEES table
DNull lock on the row being updated

Explanation

In Oracle, a DML operation such as UPDATE acquires a row-level exclusive lock on the specific row being modified, not the entire table.

Common mistakes.

A. Oracle does not acquire an exclusive table-level lock for standard DML operations; table-level locks prevent all concurrent access and are contrary to Oracle's row-level locking architecture.
C. Null locks in Oracle's lock hierarchy represent no lock held and are used in distributed lock management context, not for active DML operations on a table.
D. A null lock indicates no resource is held at the row level; a row being actively updated by a transaction holds an exclusive row lock, not a null lock.

Concept tested. Oracle row-level locking during DML operations

Reference. https://docs.oracle.com/en/database/oracle/oracle-database/19/cncpt/data-concurrency-and-consistency.html

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