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In Database Management system, A Transaction is a single unit of many logical operations/work. In simple words, Any logical calculations done in a consistent mode in Database is known as Transaction. Best one example is, ATM that we use on regular basis.



Let us understand with this table :-

Table for how the transactions processes in phases -
Person A with Having 300 Rs

and have supposed to receive 100 Rs from Person B

Person B with having 200 Rs and wants to transfer 100 Rs to Person A
R(A);// Reading the data of A R(B); // Reading the data of B
A= A+ 100; // Plus in total of A B= B-100; // Minus in total of B
W(A); //Writing the data of A W(B); //Writing the data of B
R(A) ; // Output comes as 400 Rs R(B); // Output comes as 100 Rs.





  1. Debit $100 to Groceries Expense Account
  2. Credit $100 to Checking Account


Transactional databasesEdit

A transactional database is a DBMS where that provides the ACID properties for a bracketed set of database operations (begin-commit). All the write transactions within a transaction have an all-or-nothing effect, that is, either the transaction succeeds and all updates take effect, or otherwise, the database is brought to a state that does not include any of the updates of the transaction. Transactions also take care that the effect of concurrent transactions satisfies certain guarantees known as isolation level. The highest isolation level is serializability that guarantees that the effect of concurrent transactions is equivalent to a serial (i.e. sequential) execution of them.

Most modern relational database management systems fall into the category of databases that support transactions. A new category of data stores known as NoSQL data stores has emerged during the last decade. NoSQL data stores pursue scalability and due to the lack of scalable solutions for transactional processing they renounced to provide transactions and therefore to guarantee data consistency in the advent of updates and concurrent accesses.


  1. Begin the transaction
  2. Execute a set of data manipulations and/or queries




In SQLEdit

Transactions are available in most SQL database implementations, though with varying levels of robustness. (MySQL, for example, began supporting transactions from version 5.5, with the switch to the InnoDB storage engine. The previously used storage engine, MyISAM did not support transactions.)



Object databasesEdit

Relational databases traditionally comprise tables with fixed size fields and thus records. Object databases comprise variable sized blobs (possibly incorporating a mime-type or serialized). The fundamental similarity though is the start and the commit or rollback.

After starting a transaction, database records or objects are locked, either read-only or read-write. Reads and writes can then occur. Once the user (and application) is happy, changes are committed or rolled-back atomically, such that at the end of the transaction there is no inconsistency.

Distributed transactionsEdit


Transactional filesystemsEdit


See alsoEdit


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Further readingEdit

External linksEdit