Undo data operations - Oracle Tablespaces

Q.  Which operations require undo data?
- Published on 27 Jul 15

a. Committing a transaction
b. Rolling back a transaction
c. Recovering from failed transactions
d. Both B & C
e. Both A & B

ANSWER: Both B & C


  • Nirja Shah   -Posted on 31 Aug 15
    - Oracle Database creates and manages information that is used to roll back, or undo, changes to the database.

    - Such information consists of records of the actions of transactions, primarily before they are committed.

    - These records are collectively referred to as undo.

    - Undo records are used to:

    1. Roll back transactions when a ROLLBACK statement is issued
    2. Recover the database
    3. Provide read consistency
    4. Analyze data as of an earlier point in time by using Oracle Flashback Query
    5. Recover from logical corruptions using Oracle Flashback features

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