Author Question: In Oracle Database recovery facilities, OnLine ReDo files are backup log files maintained separately ... (Read 180 times)

leo leo · **on:** Jul 7, 2018

In Oracle Database recovery facilities, OnLine ReDo files are backup log files maintained separately and not necessarily on disk media.

Indicate whether the statement is true or false

Question 2

Briefly define the four isolation levels and the problems they prevent.

What will be an ideal response?

dyrone · **Reply #1 on:** Jul 7, 2018

Answer to Question 1

FALSE

Answer to Question 2

The four isolation levels are read uncommitted, read committed, repeatable read and serializable. The three problems that can occur because of concurrent processing are dirty reads, nonrepeatable reads, and phantom reads. The read uncommitted isolation level does not prevent any of these problems from occurring. The read committed isolation level prevents dirty reads. The repeatable read isolation level prevents dirty reads and nonrepeatable reads. The serializable isolation level prevents all three problems from occurring.