Serialisable schedules, Database Management System

Assignment Help:

Serialisable Schedules:If the processes of two transactions conflict with each other, how to verify that no concurrency related problems have happened? For this, serialisability theory has been developed. Serialisability theory attempts to verify the correctness of the schedules. The rule of this theory is:

"A schedule S of n transactions is serialisable if it is equal to some serial schedule of the similar 'n' transactions".

A serial schedule is a schedule in which either transaction T1 is totally done before T2 or transaction T2  is totally done before T1. For instance, the following figure clears the two possible serial schedules of transactions T1  & T2.

Schedule A: T2 followed by T1

Schedule B: T1 followed by T2

Schedule

T1

T2

Schedule

T1

T2

Read X

 

Read X

Read X

Read X

 

Read Y

 

Read Y

Subtract 100

Subtract 100

 

Display X+Y

 

Display X+Y

Write X

Write X

 

Read X

Read X

 

Read Y

Read Y

 

Subtract 100

Subtract 100

 

Add 100

Add 100

 

Write X

Write X

 

Write Y

Write Y

 

Read Y

Read Y

 

Read X

 

Read X

Add 100

Add 100

 

Read Y

 

Read Y

Write Y

Write Y

 

Display X+Y

 

Display X+Y

                                                                         Figure: Serial Schedule of two transactions

Schedule C: An Interleaved Schedule

Schedule

T1

T2

Read X

Read X

 

Subtract 100

Subtract 100

 

Read X

 

Read X

Write X

Write X

 

Read Y

 

Read Y

Read Y

Read Y

 

Add 100

Add 100

 

Display X+Y

 

Display X+Y

Write Y

Write Y

 

                                                                           Figure: An Interleaved Schedule

Now, we have to figure out whether this interleaved schedule would be performing read and write in the same order as that of a serial schedule. If it does, then it is equivalent to a serial schedule, otherwise not. In case it is not equivalent to a serial schedule, then it may result in problems due to concurrent transactions.


Related Discussions:- Serialisable schedules

Datawarehouse, How to define a job scheduling strategy that will meet busin...

How to define a job scheduling strategy that will meet business requirement of reporting availability by 6am CST for the following cubes? Show the job scheduling dependencies in a

What is repository?, Problem 1 Why are the operational system keys not ...

Problem 1 Why are the operational system keys not recommended for forming data warehouse primary keys? Give any two examples 2 Explain the following performance tuning techn

Keys, it can be possible to create any table without primary key

it can be possible to create any table without primary key

Sources of utilities for a dbms, There are three main sources of utilities ...

There are three main sources of utilities and applications for a DBMS: a. Vendor applications and utilities are given for working with or maintaining the database, and generally

Prepare heart failure registry database, Prepare Heart Failure Registry dat...

Prepare Heart Failure Registry database How are you today? Please I would like you to design a Heart Failure registry where doctors will log in to enter information about their

Logical entity relationship diagrams, How can i turn a conceptual entity re...

How can i turn a conceptual entity relationship diagram into a logical entity relationship diagram? what do i have to do with "mandetory or" and "optional or" relationships?

State the object design for processing, State the Object Design for Process...

State the Object Design for Processing  The object design phase comes after analysis and system design phase. The object design phase includes implementation details like as i

Log, what is the need of a log in dbms

what is the need of a log in dbms

Explain the advantages of database management system, Advantages of Databas...

Advantages of Database management system Let us summarize the advantages. Reduction of Redundancy: This is perhaps the most important advantage of using DBMS. Redundancy i

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd