OCP CBT Question 591

Please solve the following question.

A user executes a long-running query on a table while concurrent DML operations are occurring. What mechanism does Oracle use to ensure the query sees a consistent view of the data as it existed when the query started?

Understanding how Oracle manages read consistency without blocking writers is fundamental to its high concurrency architecture.

Table-level locks on the queried table.

Waiting for all active DML operations to commit.

Using data from UNDO segments to reconstruct past versions of blocks.

Blocking all new DML operations until the query completes.