Distributed Databases Questions Medium
Data concurrency control in distributed databases refers to the management and coordination of concurrent access to data by multiple users or processes in a distributed environment. It ensures that transactions executed concurrently do not interfere with each other and maintain the consistency and integrity of the data.
Concurrency control mechanisms in distributed databases aim to prevent conflicts such as data inconsistency, lost updates, and dirty reads that can occur when multiple transactions access and modify the same data simultaneously. These mechanisms typically involve techniques such as locking, timestamp ordering, and optimistic concurrency control.
Locking is a commonly used technique where transactions acquire locks on data items to prevent other transactions from accessing or modifying them until the lock is released. This ensures that only one transaction can access a particular data item at a time, preventing conflicts and maintaining data consistency.
Timestamp ordering is another approach where each transaction is assigned a unique timestamp, and the execution order of transactions is determined based on these timestamps. Transactions with earlier timestamps are executed first, ensuring that conflicts are avoided and data consistency is maintained.
Optimistic concurrency control is a technique that assumes conflicts are rare and allows transactions to proceed concurrently without acquiring locks. However, before committing, each transaction is checked for conflicts with other concurrent transactions. If conflicts are detected, appropriate actions such as aborting or rolling back the transaction are taken to maintain data consistency.
In a distributed database environment, data concurrency control becomes more complex due to the involvement of multiple sites and the need for coordination among them. Various protocols and algorithms, such as two-phase locking, distributed timestamp ordering, and distributed optimistic concurrency control, are used to ensure proper coordination and synchronization among the distributed components.
Overall, data concurrency control in distributed databases is crucial for maintaining data consistency, integrity, and preventing conflicts that can arise due to concurrent access and modification of data by multiple users or processes.