Database Management (Unit-5) | 4331603
Unit - 5: Transaction Management (Marks-10)
What is transaction? 02
Transaction
A transaction is a sequence of operations performed as a single logical unit of work.
A transaction is a logical unit of work that contains one or more SQL statements.
It transforms a database from its one consistent state to another state. During the transaction,
intermediate state may be consistent or not but final state must be a consistent state.
A transaction is an atomic unit meaning that it must be either entirely completed or aborted.
Explain ACID property of a transaction. 04
State the full form of ACID properties. 02
Explain Atomicity. Why it is important? Explain with example. 02
Transaction remains in consistent state for that it must have following four properties:
1) Atomicity
2) Consistency
3) Isolation
4) Durability
These properties are called ACID property of a transaction.
ACID property of transaction
1. Atomicity -This property requires that all the operations of a transaction are
executed or not a single operation is executed.
o Means, a transaction must be completely successful 100% or fail0% without
doing anything.
o For example, consider transaction to transfer Rs.50 from account A to account B:
In above transaction if Rs. 50 is debited from account A then it must be added to
account B.
Department of Information Technology [Ms. Nikita A. Patel] 1
, Database Management (Unit-5) | 4331603
2. Consistency - A transaction must transform the database form one consistent state to
another consistent state. Means our database must remain in consistent state after
execution of any transaction.
o In above example total of A and B must remain same before and after the
execution of transaction.
3. Isolation - All transactions execute concurrently are isolated from one another.
o Updates on data made by one transaction cannot be seen by other transactions until
that transaction commits. Thus, transactions do not interfere with each other.
o In above example once your transaction start from step one its result should not be
access by any other transaction until last step (step 6) is completed.
4. Durability - Once a transaction is committed, changes made by that transaction
cannot be lost even if the system fails.
o Once your transaction completed up to step 6 its result must be stored permanently. It should not
be removed if system fails.
Draw and Explain state transition diagram. 04
State transition Diagram:
1. Active- This is the initial state. The transaction stay in this state while it is executing.
Various read and write operations are performed on database.
2. Partially Committed - When transaction ends, all write and read operations are performed, it moves to
partially committed state.
3. Committed - The state after successful completion of the transaction. It can be ensure that it will never
be aborted.
4. Aborted (Failed) - A transaction may be aborted if system failure or unrecoverable errors.
The state after the transaction has been rolled back and the database has been restored to its state prior to
the start of the transaction.
Aborted transaction can be restart later either automatically or manually.
Department of Information Technology [Ms. Nikita A. Patel] 2
Unit - 5: Transaction Management (Marks-10)
What is transaction? 02
Transaction
A transaction is a sequence of operations performed as a single logical unit of work.
A transaction is a logical unit of work that contains one or more SQL statements.
It transforms a database from its one consistent state to another state. During the transaction,
intermediate state may be consistent or not but final state must be a consistent state.
A transaction is an atomic unit meaning that it must be either entirely completed or aborted.
Explain ACID property of a transaction. 04
State the full form of ACID properties. 02
Explain Atomicity. Why it is important? Explain with example. 02
Transaction remains in consistent state for that it must have following four properties:
1) Atomicity
2) Consistency
3) Isolation
4) Durability
These properties are called ACID property of a transaction.
ACID property of transaction
1. Atomicity -This property requires that all the operations of a transaction are
executed or not a single operation is executed.
o Means, a transaction must be completely successful 100% or fail0% without
doing anything.
o For example, consider transaction to transfer Rs.50 from account A to account B:
In above transaction if Rs. 50 is debited from account A then it must be added to
account B.
Department of Information Technology [Ms. Nikita A. Patel] 1
, Database Management (Unit-5) | 4331603
2. Consistency - A transaction must transform the database form one consistent state to
another consistent state. Means our database must remain in consistent state after
execution of any transaction.
o In above example total of A and B must remain same before and after the
execution of transaction.
3. Isolation - All transactions execute concurrently are isolated from one another.
o Updates on data made by one transaction cannot be seen by other transactions until
that transaction commits. Thus, transactions do not interfere with each other.
o In above example once your transaction start from step one its result should not be
access by any other transaction until last step (step 6) is completed.
4. Durability - Once a transaction is committed, changes made by that transaction
cannot be lost even if the system fails.
o Once your transaction completed up to step 6 its result must be stored permanently. It should not
be removed if system fails.
Draw and Explain state transition diagram. 04
State transition Diagram:
1. Active- This is the initial state. The transaction stay in this state while it is executing.
Various read and write operations are performed on database.
2. Partially Committed - When transaction ends, all write and read operations are performed, it moves to
partially committed state.
3. Committed - The state after successful completion of the transaction. It can be ensure that it will never
be aborted.
4. Aborted (Failed) - A transaction may be aborted if system failure or unrecoverable errors.
The state after the transaction has been rolled back and the database has been restored to its state prior to
the start of the transaction.
Aborted transaction can be restart later either automatically or manually.
Department of Information Technology [Ms. Nikita A. Patel] 2
