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Conflict Serializability

There are two types of conflicts. In this article, we are going to learn about Conflict Serializability. Before that, let’s see what both the conflicts are.

Conflict Equivalent: If a schedule-S can be transformed into a schedule-S’ by a series of non-conflicting instructions, then S and S’ are said to be ‘Conflict equivalent’.

Conflict Serializable: A schedule-S is said to be ‘conflict serializable’, if it is conflict equivalent to a serial schedule.

 

Example-1: Create schedule-5 which is equivalent to schedule-3 part 3 of Transaction Isolation.

 

T1T2
read A;

write A;

read A;

write A;

read B;

write B;

read B;

write B;

By swapping the 4 and 5 instructions which are non-conflicting, we can get:

 

T1T2
read A;

write A;

read A;
read B;
write A;
write B;
read B;

write B;

By swapping the 5 and 6 instructions which are non-conflicting, we can get schedule-6 (T1, T2) :

 

T1T2
read A;

write A;

read B;

write B;

read A;

write A;

read B;

write B;

This is equivalent to schedule-1.

 

 

 

Findings :

   Here, schedule-5 and schedule-1 are conflict equivalents.

 Here,  schedule-1 is a serial schedule.

   So,  schedule-5  is said to be conflict serializable.

   This concept is called ‘Conflict Serializability’.

 

Reference Links

Conflict Serializability