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INTERVIEW QUESTIONS
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EJB
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Question: What is ACID?
Answer: Database transactions must be Atomic, Consistent, Isolated, and Durable (ACID). These ACID properties keep the database in a stable state. The following list details these ACID properties:
* Atomicity: All changes are committed or all changes are rolled back. No single part of the transaction is saved without all parts of the transaction. No single part of the transaction is skipped without all being skipped.
* Consistency: The database is left in a consistent state. The transaction must obey integrity constraints. If you have set a constraint that no employee shall be added to the Employees table without an entry in the Payroll table, then the database is not consistent if there is an employee in the Employees table and none in the Payroll table.
* Isolation: Transactions shall operate independently of each other. Never can one transaction see a half-finished second transaction. One transaction cannot be affected by a second transaction until the first is completed.
* Durable: Once the transaction is committed, it is saved. Even if there is a system failure, that transaction is saved. It will not be lost.
Submitted by Srinivas Vemula ([email protected])
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EJB Interview Questions & Answers -
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Question:
What is ACID?
Answer:
Database transactions must be Atomic, Consistent, Isolated, and Durable (ACID). These ACID properties keep the database in a stable state. The following list details these ACID properties:
* Atomicity: All changes are committed or all changes are rolled back. No single part of the transaction is saved without all parts of the transaction. No single part of the transaction is skipped without all being skipped.
* Consistency: The database is left in a consistent state. The transaction must obey integrity constraints. If you have set a constraint that no employee shall be added to the Employees table without an entry in the Payroll table, then the database is not consistent if there is an employee in the Employees table and none in the Payroll table.
* Isolation: Transactions shall operate independently of each other. Never can one transaction see a half-finished second transaction. One transaction cannot be affected by a second transaction until the first is completed.
* Durable: Once the transaction is committed, it is saved. Even if there is a system failure, that transaction is saved. It will not be lost.
Submitted by Srinivas Vemula ([email protected]) Source: CoolInterview.com
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