What is a transaction and what are ACID properties?
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Answer Posted / kumar
The ACID model is one of the oldest and most important
concepts of database theory. It sets forward four goals
that every database management system must strive to
achieve: atomicity, consistency, isolation and durability.
No database that fails to meet any of these four goals can
be considered reliable.
•Atomicity states that database modifications must follow
an “all or nothing” rule. Each transaction is said to
be “atomic.” If one part of the transaction fails, the
entire transaction fails. It is critical that the database
management system maintain the atomic nature of
transactions in spite of any DBMS, operating system or
hardware failure.
•Consistency states that only valid data will be written to
the database. If, for some reason, a transaction is
executed that violates the database’s consistency rules,
the entire transaction will be rolled back and the database
will be restored to a state consistent with those rules. On
the other hand, if a transaction successfully executes, it
will take the database from one state that is consistent
with the rules to another state that is also consistent
with the rules.
•Isolation requires that multiple transactions occurring at
the same time not impact each other’s execution.
.Durability ensures that any transaction committed to the
database will not be lost. Durability is ensured through
the use of database backups and transaction logs that
facilitate the restoration of committed transactions in
spite of any subsequent software or hardware failures
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