Answer to Question #266596 in Databases | SQL | Oracle | MS Access for saurav kumar

Question

Q1. (a) What is Serializability?Explain different types of Serializability.

(b) Check the given schedule for conflict serializability:

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

All the steps for checking the serializability should be written properly and diagram should be drawn well if any

Answer 1

A schedule is called as thee serialized if it is equivalent to serial schedule. It mens the concurrent schedule which execute one by one serially can be known as the serialized schedule. It refers to the sequence of actions such as read, write, commit, abort etc are performed in the serial manner.

There are two types of serializability -

- View Serializability

- Conflict serializability

View serializability : A schedule can be says ass the view serializable if it is viewed equivalent to serial schdue.

There are three rules in the view serializability, let T1 and T2 be transaction then

• T1 is reading the initial value of A then T2 also reads the initial value of A.
• T1 is the reading value written by T2 then T2 also reads the value written by T1
• If T1 is writing the final value then T2 also has thee write operation as the final value.

Conflict serializability:

It orders the conflicting operation in the same way as some serial execution. A pair of operation is said to conflict if they operate on the same data and one of them is write operation.

• Read A(x) Read B(x) - non conflict because it is read read operation
• Read A(x) write B(x) - conflict read-write operation
• write A(x) read B(x) - conflict write -read operation
• write A(x) write B(x) - conflict write write operation

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

Here we can see that it is following all the conditions of the view serializability

All thee operation is getting follow by the transaction T2 which T1 is doing.

So, we can say that it is view seriaizabl.