What is a transaction?

The Transaction is a unit of data processing. For instance, many of the transactions at a bank may be withdrawal or deposit of money; transfer of money from A's account to B's account etc. A transaction would include manipulation of one or more data values in a database. Therefore, it may need reading and writing of database value. For instance, the withdrawal transactions can be written in pseudo code as:

Example:

; Suppose that we are doing this transaction for person

;  whose account number is X.

TRANSACTION WITHDRAWAL (withdrawal_amount)

start transaction

IF X exist then

READ  X.balance

IF   X.balance > withdrawal_amount THEN

 SUBTRACT withdrawal_amount

WRITE X.balance

COMMIT

ELSE

         DISPLAY "TRANSACTION CANNOT BE PROCESSED"

 ELSE DISPLAY "ACCOUNT X DOES NOT EXIST"

End transaction;

Another same example may be transmitting of money from Account no x to account number y. This transaction may be written as: