The start of execution/invocation of a particular sub-system/task/feature of the SUT
by a pre-specified number of users (the workload) within the same brief time window (1-3 seconds) is termed as simultaneous usage of the system. This is usually accomplished by employing timing and synchronization features in workload generation tools - e.g. Rendezvous points in LoadRunner∞
enable one to synchronize users in a scenario for simultaneous usage.
Simultaneous usage may not always be reflective of actual usage and is to be used sparingly.