Mumbai University > Information Technology > Sem 3 > Database Management System

Marks: 2 M

Year: Dec 2014

SCHEDULE:
A sequences of instructions that specify the chronological order in which instructions of concurrent transactions are executed.

A schedule for a set of transactions must consist of all instructions of those transactions. It must preserve the order in which the instructions appear in each individual transaction. A transaction that successfully completes its execution will have a commit instructions as the last statement (will be omitted if it is obvious). A transaction that fails to successfully complete its execution will have an abort instructions as the last statement (will be omitted if it is obvious).

Example:

• Let T1 transfer $50 from A to B, and T2 transfer 10% of the balance from A to B.
• A serial schedule in which T1 is followed by T2:

• A schedule is serial schedule where instructions belonging to one transaction appear together.
• For a set of n transaction, there exist n! different valid serial schedules.