Description: Isolation level is a configuration that determines how the integrity of a transaction is visible to other transactions. In the context of databases and transaction management systems, isolation refers to the ability of a transaction to operate independently of other concurrent transactions. This is crucial for ensuring data consistency and integrity, especially in environments where multiple users or processes may be accessing and modifying the same information simultaneously. There are several isolation levels, ranging from the most restrictive, where transactions are completely independent, to the most permissive, where transactions can see changes made by others before they are completed. Isolation levels are commonly defined in terms of four properties: dirty read, non-repeatable read, repeatable read, and serializability. Each of these levels offers a different balance between data consistency and system performance, allowing developers and database administrators to choose the most appropriate level based on the specific needs of their applications.
History: The concept of isolation levels was formalized in the context of relational databases in the 1970s, with the development of the transaction model by Edgar F. Codd, who is known for his work on the relational model. In 1981, Codd introduced the rules of transactions, which included isolation as one of the fundamental properties. Over the years, different models and standards, such as SQL, have defined and standardized isolation levels in database systems.
Uses: Isolation levels are primarily used in database management systems to control how transactions interact with each other. This is especially important in critical applications where data integrity is paramount, such as in banking, reservation, and inventory management systems. Developers can choose the appropriate isolation level to optimize the performance and consistency of their applications.
Examples: A practical example of using isolation levels is in a flight reservation system. If two users attempt to book the same seat at the same time, a high isolation level (such as serialization) will ensure that only one of them can complete the transaction, thus preventing overselling. On the other hand, a lower isolation level might allow both users to see the seat as available, which could lead to conflicts.
