Question

Define concurrency control and explain its need in any transaction. What are the major goals and mechanisms of concurrency control

Answer 1

Answer:

concurrent control can be defined as a feature in DBMS which allows multiple transaction to access and modify share data at the same time without violating the data integrity...however disability is not exhibited by traditional file processing system where multiple access to same data cause data inconsistencies....

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Answer 2

Answer:

The goal of concurrency control is to coordinate execution so that the VIEW or effect from the database's perspective is the same as if the concurrently executing transactions were executed in a serial fashion. This scheme is referred to as the serializable execution of transactions.

Explanation:

Concurrency Control is the working concept that is required for controlling and managing the concurrent execution of database operations and thus avoiding inconsistencies in the database. Thus, for maintaining the concurrency of the database, we have the concurrency control protocols.

Concurrency control is provided in a database to:

1. enforce isolation among transactions.
2. preserve database consistency through consistency preserving execution of transactions.
3. resolve read-write and write-read conflicts.

Concurrency control is used to apply isolation through mutual exclusion. It ensures serialization in the system. It preserves data consistency and resolves the conflict during read-write operations.  Time stamp ordering ensures both conflict serializability and freedom from deadlock as timestamp-based concurrency control is a non-lock concurrency control method.