DBMS-Transactions-Revision

RAID stand for _________

• Redundant Arrays of Idempotent Data

• Redundant Arrays of Independent Disks

• Redundant Arrays of Independent Data

• Redundant Arrays of Isolated Disks

The files with variable length records make use of _________ structure for storage.

To preserve the integrity and consistency of data, the database system must ensure

• Atomicity

• Isolation

• Durability

• Consistency

• All of the above

Consider the following action:

TRANSACTION.....

Commit;

ROLLBACK;

What does Rollback do?

• Undoes the transactions before commit

• Clears all transactions

• Redoes the transactions before commit

• No action

If a schedule S can be transformed into a schedule S' by a series of swaps of non-conflicting instructions, we say that S and S' are

• Conflict serializable

• Conflict equivalent

• View serializable

• Serializable

Consider the two transactions T1 and T2 and four schedules S1, S2, S3, S4 of T1 and T2 as given below

S1: R1(X); R2(X); R2(Y); W1(X); W1(Y); W2(Y)

S2: R1(X); R2(X); R2(Y); W1(X); W2(Y); W1(Y)

Here R1(X) denotes read operation on X by the transaction T1 and W1(X) denotes write operation on X by the transaction T1.

Which of the schedules(s) are conflicts serializable?

• S1 and S2

• S2 only

• S1 only

• Neither S1 nor S2

For the given schedule, which is the equivalent serial schedule?

• T1 - T2 - T3

• T1 - T3 - T2

• T2 - T1 - T3

• T3 - T1 - T2

The column ‘C’ has to be indexed. What is the content of the bitmap index?

A B C

a1 b1 c2

a1 b1 c2

a2 b4 c1

a3 b2 c3

Identify the options which are true for Immediate-modification scheme

• Allows updates of an uncommitted transaction to be made to the buffer, or the disk itself, before the transaction commits.

• Update log record must be written after a database item is written

• Output of updated blocks to disk storage can take place at any time before or after transaction commit

• Performs updates to buffer/disk only at the time of transaction commit

Consider the state of the transactions in the diagram and the statements given below:

A. T1 can be ignored.

B. T2 and T3 redone

C. T4 undone

D. T4 redone

Mark the correct group of statements from the options below

• A, B, D

• A, B, C

• Only A and B but not C

• Only B and C but not A