How do you handle database conflicts when multiple users access the same data?

1 Types of database conflicts

Database conflicts can be classified into two main types: read-write conflicts and write-write conflicts. Read-write conflicts happen when one user reads data while another user updates or deletes the same data, leading to stale or outdated data. Write-write conflicts happen when two or more users try to update or delete the same data, leading to conflicting or duplicate data. Depending on the nature and frequency of the database operations, the impact of database conflicts can vary from minor to severe.

2 Causes of database conflicts

Database conflicts are caused by various factors, such as concurrency, isolation, replication, and synchronization. Concurrency refers to the ability of multiple users to access or modify the same data simultaneously. Isolation refers to the degree of separation between different transactions or operations on the same data. Replication refers to the process of copying or distributing data across multiple servers or locations. Synchronization refers to the process of ensuring that replicated data are consistent and up-to-date. These factors can affect the performance, availability, and integrity of the database.

3 Solutions for database conflicts

Database conflicts can be prevented or resolved by using different techniques, such as locking, versioning, timestamping, and conflict resolution policies. Locking is a mechanism that restricts access or modification of data by other users while one user is using it. Versioning is a mechanism that assigns a unique identifier or number to each version of data, allowing users to track changes and compare differences. Timestamping is a mechanism that records the time of each operation on data, allowing users to determine the order and validity of operations. Conflict resolution policies are rules or algorithms that decide how to handle conflicting or duplicate data, such as choosing the latest, the majority, or the user-defined value.

4 Locking techniques

Locking techniques can be divided into two categories: pessimistic locking and optimistic locking. Pessimistic locking assumes that database conflicts are likely to occur and locks data before accessing or modifying it, preventing other users from using it until the lock is released. Optimistic locking assumes that database conflicts are rare and does not lock data until the end of the operation, allowing other users to use it concurrently. However, if a conflict is detected, the operation is aborted and the user has to retry or cancel it.

5 Versioning techniques

Versioning techniques can be divided into two categories: multiversion concurrency control (MVCC) and distributed version control (DVC). MVCC is a technique that allows multiple versions of data to coexist in the database, enabling users to read or write data without locking it. Each version of data has a version number and a validity range, indicating when it was created and when it was modified or deleted. DVC is a technique that allows users to create and manage their own copies or branches of data, enabling users to work offline or collaboratively. Each copy or branch of data has a unique identifier and a history of changes, allowing users to merge or synchronize data.

6 Timestamping techniques

Timestamping techniques can be divided into two categories: logical timestamping and physical timestamping. Logical timestamping is a technique that assigns a logical value, such as a counter or a vector, to each operation on data, indicating its relative order and causality. Logical timestamping does not depend on the actual time or clock of the system, but on the logical rules or protocols of the database. Physical timestamping is a technique that assigns a physical value, such as a date or a time, to each operation on data, indicating its absolute order and validity. Physical timestamping depends on the actual time or clock of the system, but may require synchronization or coordination among different servers or locations.

7 Here’s what else to consider

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