Transactions in DBMS, Define transaction in database, Explain database transactions with example
Transactions
Transaction is a logical unit of
work carried out by a single execution (of a program
or an application) that reads or writes (updates/changes) the contents’ (one or more data items) values of the database.
Discussion:
Example 1
Assume that you have a savings
account with account number ‘A101’ and you want to check your latest account
balance. Here,
Data Item(s): Your account with
account number ‘A101’ is the data item.
Operation (Read/Write): You want to access your balance. That
means you like to read the balance.
Program/Application: You may use, for
example, the ATM machine interface. That is the application/program which does
read your balance from database.
Example 2
Assume that you want to transfer
money from your account ‘A101’ to your friend’s account ‘A345’. Here,
Data Item(s): Your account with
account number ‘A101’ is one data item. Your friend’s account ‘A345’ is
another data
item.
Operation (Read/Write): You want to transfer fund from your
account to others. This action reduces your balance and increases your
friend’s. This means you have to write new balances in both data items.
Program/Application: You may use, for
example, the internet banking facility. Here, internet banking is the application/program which does change (write)
your balances in the database.
Other definitions:
A transaction is a unit of
program execution that accesses and possibly updates various data items – Silberschatz,
Korth, Sudarshan - Database System Concepts.
A transaction symbolizes a unit of
work performed within a database management system (or similar system) against
a database, and treated in a coherent and reliable way independent of other
transactions. A transaction generally represents any change in database - Wikipedia.
A transaction is an executing
program that forms a logical unit of database processing. A transaction
includes one or more database access operations—these can include insertion,
deletion, modification, or retrieval operations - Ramez Elmasri, Shamkant
B. Navathe - Fundamentals of Database Systems.
A transaction is defined as any one
execution of a user program in a DBMS. A transaction is seen by the DBMS as a
series, or list, of actions. The actions that can be executed by a transaction
include reads and writes of database objects. A transaction can also be defined
as a set of actions that are partially ordered. That is, the relative order of
some of the actions may not be important – Raghu
Ramakrishnan, Johannes Gehrke – Database Management Systems.
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