Unrepeatable reads-problems of concurrent transactions, Database Management System

Assignment Help:

Unrepeatable reads: Assume T7 reads X twice during its implementation. If it did not update X itself it could be very disturbing to see a dissimilar value of X in its next read. But this could occur if, among the two read operations, another transaction modifies X.

 

T7

T8

Assumed value of

X=2000

T7

T8

READ X

 

2000

 

 

UPDATE X

 

3000

READ X

 

3000

 

 

Therefore, the inconsistent values are read and results of the transaction may be in fault.

 


Related Discussions:- Unrepeatable reads-problems of concurrent transactions

Mappings between levels and data independence, Mappings between Levels and ...

Mappings between Levels and Data Independence The 3 levels of abstraction in the database do not exist separately of each other. There must be some correspondence, or mapping

When is update_statistics command used, When is UPDATE_STATISTICS command u...

When is UPDATE_STATISTICS command used? - When processing of large data is done, this command is used. - Whenever large number of modification, deletions or copy takes place

Spanned and unspanned organisation, Spanned and unspanned organisation? ...

Spanned and unspanned organisation? Spanned and unspanned organization: If records are not permited to cross block boundaries then the organisation is called unspanned record

Draw the architecture of mysql, Data Base Management System 1. Draw the...

Data Base Management System 1. Draw the Architecture of MySQL and explain about its subsystems briefly. 2. Elaborate with the help of an example the concept of Primary key a

Explain group by clause in sql, Explain group By clause in SQL? Group B...

Explain group By clause in SQL? Group By clause in SQL: The GROUP BY clause can be used in a SELECT statement to collect data across multiple records and group the results thro

Define the concept of aggregation, Define the concept of aggregation.  Give...

Define the concept of aggregation.  Give two examples where this concept is useful. Ans: Aggregation transforms a relationship among the objects into a higher-level object. A

What are the several kinds of the update operations relation, What are the ...

What are the several kinds of the update operations on relations? Also explain the constraints on these update operation. Give instance in support of your answer. There are th

Post vbulletin hack and new server problem, Project Description: My VBul...

Project Description: My VBulletin forum was hacked, and soon after my server machine died. So, I'm now on a new machine, and I think that I've taken care of 99% of the hacking..

ER Diagram, Soccer player ER Diagram to Relational database schema

Soccer player ER Diagram to Relational database schema

Explain relational model and their use in dbms, Explain Relational model an...

Explain Relational model and their use in DBMS? Relational Model - The relational model was first introduced through E.F. Codd of the IBM Research in the year of 1970. The mode

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