The concurrent transactions, Database Management System

The Concurrent Transactions

 Almost every commercial DBMS support multi-user environment. Therefore, allowing multiple transactions to proceed concurrently. The DBMS must make sure that two or more transactions do not obtain into each other's way, i.e., transaction of one user doesn't effect the transaction of other or even the transactions issued by the similar user should not get into the way of each other. Be advised that concurrency related problem may happen in databases only if two transactions are contending for the similar data item and at least one of the concurrent transactions wishes to update a data value in the database. In this, the concurrent transactions only read similar data item and no updates are done on these values, then it does NOT create any concurrency related difficulty. Now, let us talk about why you require a mechanism to control concurrency.

Consider a banking application dealing with saving and checking accounts. A Banking Transaction T1 for Mr. Sharma moves Rs.100 from his checking account balance X to his savings account balance Y, using the transaction T1:

Transaction T1:

A:  Read X

Subtract 100

Write X

B:   Read Y

 Add 100

Write Y

Let us assume an auditor wants to know the total assets of Mr. Sharma. He implements the following transaction:

Transaction T2:

Read X Read

Y Display

X+Y

Assume both of these transactions are issued concurrently, and then the implement of these instructions can be combined in many ways. This is also known as the Schedule. Let us describe this term in more detail.

A schedule S is described as the sequential ordering of the operations of the 'n' interleaved transactions. A schedule keeps the order of operations within the individual transaction.

 

                       5_The Concurrent Transactions.png

                   One possible schedule for interleaved execution of TA and TB

Posted Date: 3/11/2013 5:36:08 AM | Location : United States







Related Discussions:- The concurrent transactions, Assignment Help, Ask Question on The concurrent transactions, Get Answer, Expert's Help, The concurrent transactions Discussions

Write discussion on The concurrent transactions
Your posts are moderated
Related Questions
What are the two methods for dealing deadlock problem? The two procedures for dealing deadlock problem is deadlock detection and deadlock recovery.

Shared lock or Read Lock It is requested by a transaction that needs to just read the value of data item. A shared lock on a data item does not permit an exclusive lock

Information about films holds information about movies, stars and studios. Movies have a title, year of production, length and the film type. Stars have a name and address. Studi

Define garbage collection. Garbage may be formed also as a side effect of crashes. Periodically, it is essential to find all the garbage pages and to add them to the list of fr

Explain data abstraction? Data abstraction Data abstraction is a methodology in which enables us to isolate how a compound data object is utilized from the details of how it is

Define multivalued dependency.  What do understand by trivial multivalued dependency?  Ans: A multivalued dependency is a full constraint among two sets of attributes in a rela

What is an ER diagram? Why is it used in Database management system (DBMS)?

With the help of an example display how records can be deleted and updated in QBE. (i) Increase Pay_Rate of employees along with the skill of ‘cook' by 10%. (ii) Delete employee

One-way Associations If an association is only traversed in single direction, then it is known as one-way association. It is implemented as a pointer or an attribute which con

I need ERP system We are selling automotive spare parts on the internet and we require ERP software, which would sync with our e-shop. Our e-shop doesn't use any e-commerce plat