Managing Multiuser Databases
The advantage of optimistic locking is that:

the lock is obtained before the transaction has processed.
the lock is obtained only after the transaction has processed.
transactions that are best suited are those with a lot of activity.
the lock never needs to be obtained.

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Managing Multiuser Databases
What is the overall responsibility of the DBA?

Both the first and third answers above are correct.
Facilitate the development and use of the database
Development, operation, and maintenance of the database and its applications
Create and populate tables

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