Answer Posted / vinay mishra (ucc_uor)
The ACID model is one of the oldest and most important
concepts of database theory.
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. For
example, if Joe issues a transaction against a database at
the same time that Mary issues a different transaction, both
transactions should operate on the database in an isolated
manner. The database should either perform Joe’s entire
transaction before executing Mary’s or vice-versa. This
prevents Joe’s transaction from reading intermediate data
produced as a side effect of part of Mary’s transaction that
will not eventually be committed to the database. Note that
the isolation property does not ensure which transaction
will execute first, merely that they will not interfere with
each other.
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.
| Is This Answer Correct ? | 19 Yes | 7 No |
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