A shared lock, in the context of computer science and database management, refers to a type of lock used to control concurrent access to a resource or data item by multiple users or processes. It is commonly employed in multi-user environments where data integrity and consistency need to be maintained while permitting simultaneous read operations.
When a shared lock is acquired on a resource, it allows multiple transactions to access and read the resource simultaneously. This means that multiple users can access the data concurrently without interfering with each other's operations. However, a shared lock does not grant the privilege of modifying the resource or performing write operations. It only provides a guarantee that the data read by different users remains consistent and is not modified by others during the read operation.
The shared lock differs from an exclusive lock, which grants exclusive access to a resource for a single user, preventing other users from concurrently reading or modifying the data. With shared locks, multiple users can simultaneously read the resource, making it suitable for scenarios where data integrity is maintained by prohibiting write operations while permitting concurrent read access.
Shared locks are widely used in databases and file systems to enhance concurrency and efficiency. They play a crucial role in enabling multi-user environments by providing controlled access to resources, ensuring consistency, and preventing conflicts between reading and writing operations.
The word "shared lock" can be broken down into two parts: "shared" and "lock".
The word "shared" comes from the Old English word "scearu", which meant a portion or a division. Over time, it evolved into the Middle English word "sheren", which meant to divide or distribute. The term "shared" thus refers to something that is divided or distributed among multiple parties.
The word "lock" is derived from various Old English and Germanic words, such as "loc" and "lucca", which meant a fastening device or a means of enclosure. The concept of a lock has remained consistent throughout various languages and cultures, representing a mechanism used to secure or restrict access to something.