Q. Which of the following scenarios may lead to an irrecoverable error in a database system ?

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Q. Consider the following transaction involving two bank accounts x and y.

read(x); x := x – 50; write(x); read(y); y := y + 50; write(y)

The constraint that the sum of the accounts x and y should remain constant is that of

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Q. Consider a simple checkpointing protocol and the following set of operations in the log.

(start, T4); (write, T4, y, 2, 3); (start, T1); (commit, T4); (write, T1, z, 5, 7);
(checkpoint);
(start, T2); (write, T2, x, 1, 9); (commit, T2); (start, T3); (write, T3, z, 7, 2);

If a crash happens now and the system tries to recover using both undo and redo operations, what are the contents of the undo list and the redo list

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Q. Which level of locking provides the highest degree of concurrency in a relational data base?

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Q. Which one of the following is NOT a part of the ACID properties of database transactions?

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Q. Consider the following two phase locking protocol. Suppose a transaction T accesses (for read or write operations), a certain set of objects {O1,...,Ok}. This is done in the following manner: Step 1. T acquires exclusive locks to O1, . . . , Ok in increasing order of their addresses. Step 2. The required operations are performed. Step 3. All locks are released. This protocol will

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Q. Suppose a database schedule S involves transactions T1, ....Tn. Construct the precedence graph of S with vertices representing the transactions and edges representing the conflicts. If S is serializable, which one of the following orderings of the vertices of the precedence graph is guaranteed to yield a serial schedule?

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Q. Consider the following database schedule with two transactions, T1 and T2.

S = r2(X); r1(X); r2(Y); w1(X); r1(Y); w2(X); a1; a2;

where ri(Z) denotes a read operation by transaction Ti on a variable Z, wi(Z) denotes a write operation by Ti on a variable Z and ai denotes an abort by transaction Ti . Which one of the following statements about the above schedule is TRUE?

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Q. Consider the following three schedules of transactions T1, T2 and T3. [Notation: In the following NYO represents the action Y (R for read, W for write) performed by transac­tion N on object O.]

(S1) 2RA 2WA 3RC 2WB 3WA 3WC 1RA 1RB 1WA 1WB
(S2) 3RC 2RA 2WA 2WB 3WA 1RA 1RB 1WA 1WB 3WC
(S3) 2RA 3RC 3WA 2WA 2WB 3WC 1RA 1RB 1WA 1WB

Which of the following statements is TRUE?

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Q. Which of the following statement is/are incorrect?

A: A schedule following strict two phase locking protocol is conflict serializable as well as recoverable.
B: Checkpoint in schedules are inserted to ensure recoverability.

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Q. An index is clustered, if

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Q. A clustering index is defined on the fields which are of type

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Q. A file is organized so that the ordering of data records is the same as or close to the ordering of data entries in some index. Then that index is called

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Q. Given the following input (4322, 1334, 1471, 9679, 1989, 6171, 6173, 4199) and the hash function x mod 10, which of the following statements are true?

1. 9679, 1989, 4199 hash to the same value
2. 1471, 6171 hash to the same value
3. All elements hash to the same value
4. Each element hashes to a different value

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Q. How many serial schedules are possible using n-transactions?

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Q. Which of the following is wrong?
The goal of concurrent execution is

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Q. Consider the following ordering of transactions:

T1 : R(X); T2 : R(X); T1 : w(x); T1 : r(y); T2 : w(x); T2 : Commit; T1: w(y) ; T1: Commit

Which of the following is true?

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Q. In strict two-phase locking protocol

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Q. Suppose three are 3 transactions T22, T23, T24 with timestamps 10, 20, 30. Now T23 occupies a data item that is required by T22 and T24. Among the four possibilities what will be true in wait–die schema?

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Q. Two transactions T₁ and T₂ are given as follows:

T₁: r₁ (A); w₁(A); r₁ (B); w₁(B)

Find the no. of conflict serializable schedules that can be formed over T₁ and T₂.

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