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ACID properties of databases

Description of the properties

ACID stands for
  • Atomicity
  • Consistency
  • Isolation
  • Durablity

Atomicity

Modification on the data in the database either fail or succeed. The beginning of such a modification starts with a transaction and ends when a transaction finishes (either by a commit or a rollback). A software crash entails an implicit rollback.

Consistency

Only valid data (valid according to integrity constraints) may be commited.

Isolation

One transaction does not interfere with another. The 'executor' of a transaction has the feeling that he has the entire database for himeself.

Durablity

A commited transaction will not be lost.

Technical details

Oracle uses the redo log and undo to make ACID possible.