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Topic: What is a transaction and what are ACID properties
Sachin Jain
30 Oct 2010 at 02:38 AM
What is a transaction and what are ACID properties?

Re: What is a transaction and what are ACID properties
31 Oct 2010 at 10:51 PM

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.

Total Replies: 1
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