A - Atomocity
Atomicity means all or nothing. Imagine, we have an application for a bank, and we need to implement the logic for a transfer of money from one account to another account. This procedure will reduce the balance in one account and increase the balance in another account. We have to make sure that either both these steps happen or none happen. It would be very undesirable if we reduced the balance of one account without increasing the balance of the other. If both these sql statements are executed in a transaction then we are guaranteed that either both will be executed or none will be executed, because transactions guarantee Atomicity.
C - Consistency
Imagine a forum application where we have a table for a post, and a table for user such that the post table has a foreign key for the user. What would happen if we delete a use who has several entries in the post table? We will end up with rows in the post table which no longer refer to a valid user. This violates a constraint in the post table, leaving the database in an inconsistent state. Well in an RDBMS this will not happen because it guarantees consistency.
I - Isolation
Isolation means the results of a transactions are invisible to another transaction until that transaction completes.
No comments:
Post a Comment