The simultaneous access of the same data by multiple users. In database software concurrency requires additional logic to ensure that all users see consistent data and that all changes are made in the proper order.

• 多个用户同时访问同一数据。在数据库软件中，并发运行需要附加逻辑以保证所有看到的数据是一致的，并且数据的所有修改以适当的顺序进行。