# Calculation of Serial and Non-Serial Schedules in DBMS

Last Updated : 24 Jan, 2023

The serial execution of a transaction is defined as Schedule. It is made up of a number of transactions each comprising of a number of instructions. Types of Schedules

• Serial Schedules
• Non-Serial Schedules

Calculation of Number of Schedules : Consider there to be n number of transactions t1, t2, t3, …., tN with N1,N2,N3,…..Nn number of operations respectively.

1. Total Number of Schedules –
`(N1 + N2 + N3 + ..... + Nn)! / (N1! * N2! * N3! * ... * Nn!)`
1. Number of Serial Schedules –
`It is all possible permutations of n transactions = N!`
1. Number of Non-Serial Schedules – Total Schedules = Serial Schedules + Non-Serial Schedules Number of Non-Serial Schedules = Total Number of Schedules – Number of Serial Schedules
`((N1 + N2 + N3 + ..... + Nn)! / (N1! * N2! * N3! * ... * Nn!)) - (N!)`

Example – Consider there to be three transactions with 1, 2, and 3 operations respectively. We have to find –

• Total number of schedules possible.
• Total number of serial schedules and non-serial schedules possible.

Solution – Total Number of Schedules,

```= (1 + 2 + 3)! / (1! * 2! * 3!) = 6! / 12 = 60

Number of Serial Schedules,
= 3! = 6

Number of Non-Serial Schedules,
= Total Number of Schedules - Number of Serial Schedules
= 60 - 6
= 54 ```

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