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

Objectives of data management, The traffic data mgmt. systems infrastructur...

The traffic data mgmt. systems infrastructure plan describes the software, hardware, data network, and other elements that will support the TDMS. The infrastructure plan is based o

Determine the concept of process, Determine the concept of Process Pro...

Determine the concept of Process Process: A process transforms the data values. It is represented as ellipse containing a description of transformation. Each procedure has a

What is relational model feature, What is relational model feature? A r...

What is relational model feature? A relational model feature is much more data independence than some other database models.

We need help in booking system for golf business, We need help in Booking S...

We need help in Booking System for Golf Business Development of a web based booking system which permits clients to book golf lessons with the following features- a) 4 user p

Mixed fragmentation, Mixed fragmentation: Sometimes, horizontal fragmentati...

Mixed fragmentation: Sometimes, horizontal fragmentation or vertical fragmentation of a database schema by itself is insufficient to sufficiently distribute the data for some appli

FIELDS, 4. Describe three ways to handle missing field values

4. Describe three ways to handle missing field values

What is a view, What is a view? How it is related to data independence? ...

What is a view? How it is related to data independence? A view might be thought of as a virtual table, that is, a table that does not really exist in its own right but is inste

What are the various states of transaction process, What are the various st...

What are the various states through which a transaction passes through in its lifetime?  Briefly discuss all the events that causes transition from one state to another.   Ans:

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