A transaction is a logical unit of work in which, all the 
steps must be performed or none. ACID stands for Atomicity, 
Consistency, Isolation, Durability. These are the 
properties of a transaction

A transaction is a sequence of sql Operations(commands), 
work as single atomic unit of work. To be qualify 
as "Transaction" , this sequence of operations must satisfy 
4 properties , which is knwon as ACID test.

A(Atomicity):-The sequence of operations must be atomic, 
either all or no operations are performed.

C(Consistency):- When completed, the sequence of operations 
must leave data in consistent mode. All the defined 
relations/constraints must me Maintained.

I(Isolation): A Transaction must be isolated from all other 
transactions. A transaction sees the data defore the 
operations are performed , or after all the operations has 
performed, it can't see the data in between.

D(Durability): All oprtaions must be permanently placed on 
the system. Even in the event of system failure , all the 
operations must be exhibit.

A transaction is an atomic unit of work that must be 
completed in its entirety.The transaction succeeds if it 
committed and fails if it is aborted.Transactions have four 
essential properties:atomicity,consistency,isolation, and 
durability(known as the ACID properties).

Atomicity:The work cannot be broken into smaller 
parts.Although a transaction might contain many SQL 
statements,it must be run as all-or-nothing 
proposition,which means that,if a transaction is only 
partially complete when an error occurs,the work revertss 
to its state prior to the start of the transaction.

Consistency:A transaction must operate on a consistent view 
of the data and also leave the data in a consistency 
state.Any work in progress must not be visible to other 
transactions until the transaction has been committed.

Isolation:A transaction should appear to be running by 
itself,the effects of other ongoing transactions must be 
invisible to this transaction,and the effects of this 
transaction must be invisible to other ongoing transaction.

Durability:When the transaction is committed,it must be 
persisted so it is not lost in the event of a power 
failure.Only committed transaction are recovered during 
power-up and crash recovery;uncommitted work is roll back.

A-Atomacity
C-Consistency
I-Isolation
D-Durability
Atomacity-eiher all operations of the transaction are 
reflected properly in the database are none all.
Consistency-Execution of transaction in isolation (ie)with 
no other transaction executing concurrently.preserve
the consistency of the database.
Isolation-even though multiple transaction may execute 
concurrently.
Durablity-
after a transaction complete successfully the changes it has
made to the database presist even if there are system 
failure.
These are called ACID properties.