optimistic concurrency control assumes that conflicts are rare. Transactions execute without acquiring locks during their read and write phases. Instead, they maintain a private workspace where they perform their modifications. Only at the time of commit does a transaction validate its changes against the current state of the database to ensure no conflicts have occurred.
The validation phase typically involves checking for:
- Read-Write Conflicts: Has any data accurate cleaned numbers list from frist database item read by the validating transaction been modified by a concurrently committed transaction?
- Write-Write Conflicts: Has any data item written by the validating transaction also been written by a concurrently committed transaction?
If no conflicts are detected, the transaction why phone number lists are still powerful in 2025 commits, and its changes are made permanent. If conflicts are found, the transaction is aborted and restarted. Optimistic concurrency control is well-suited for environments with low contention, as it avoids the overhead of locking. However, in high-contention scenarios, the frequent aborts can lead to poor performance.
4. Multiversion Concurrency Control (MVCC):
MVCC is a sophisticated technique that maintains european data multiple versions of data items. When a transaction modifies a data item, instead of overwriting the existing value, a new version of the item is created. Each version is typically timestamped or given a version ID. This approach allows readers to access older consistent versions of data without being blocked by writers, and writers to create new versions without blocking readers.
When a transaction needs to read a data item, it reads the appropriate version based on its own timestamp or the transaction ID. For example, a transaction might read the latest committed version that was created before its own start timestamp. When a transaction writes, it creates a new version. MVCC significantly reduces read-write contention and eliminates the need for shared locks during reads, leading to higher concurrency. Popular database systems like PostgreSQL, Oracle (using undo segments), and MySQL (with InnoDB engine) extensively utilize MVCC.