A term referring to the simultaneous access to a network resource by more than one client. Concurrency is an important issue in the licensing of a server operating system or application. For example, the Per Server licensing mode for Microsoft Windows NT Server is based on concurrency. If you purchase 10 client access licenses (CALs) for your Windows NT Server, a maximum of 10 concurrent connections can legally be formed with that server for accessing network resources.
Some products, such as Microsoft Outlook 98, do not support concurrent access. In other words, you cannot install a central copy of Outlook 98 on a server and have thin clients run this program from the centralized location. Instead, you must install one copy of Outlook 98 on each client that needs to run it.