Management Information System

AssignmentACID Test PropertiesSubmitted toMs. Maida Masood

Submitted byMuhammad Umair Roll No. 40BBA 8 (Afternoon)ACID(Atomicity,Consistency,Isolation,Durability) is a set of properties that guarantee thatdatabase transactionsare processed reliably. In the context ofdatabases, a single logical operation on the data is called a transaction. For example, a transfer of funds from one bank account to another, even involving multiple changes such as debiting one account and crediting another, is a single transaction. A transaction is a sequence of operations performed as a single logical unit of work. A logical unit of work must exhibit four properties, called the atomicity, consistency, isolation, and durability (ACID) properties, to qualify as a transaction.

Atomicity refers to a state in which either all the operations or transactions should occur or simply nothing occur. The series of operation cannot be divided or performed partially. They should be performed or are performed once in an all.

Example: if a potential customers is making a transaction like a) reserving a seat by b) paying the price. He should perform both the a & b steps or neither of the both. System will not allow passenger to only reserving the seat and not paying for it or only paying and not reserving. In both above conditions transaction will fail to proceed.

Consistency property ensures that the database remains in a consistent state before the start of the transaction and after the transaction is over (whether successful or not). It transactions violates the consistency of data, the entire transaction will be reverted.

Example: a gender column of a database may only have the values male, female or unknown. If a user attempts to enter something else, say hermaphrodite then a database consistency rule kicks in and disallows the entry of such a value.

Isolation in the context of databases specifies when and how the changes implemented in an operation become visible to other parallel operations. Transaction isolation is an important part of any transactional system.

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 Joes entire transaction before executing Marys or vice-versa.

Durability refers to the guarantee that once the user has been notified of success, the transaction will persist, and not be undone. This means it will survive system failure, and that the database system has checked the integrity constraints and won't need to abort the transaction.

Example: For example, if a flight booking reports that a seat has successfully been booked, then the seat will remain booked even if the system crashes.