Virtual shared memory (VSM) is a technique through which multiple processors within a distributed computing architecture are provided with an abstract shared memory. It is a data processing technique designed to eliminate the additional processor-to-processor communication required within distributed computing, such as when the new value of a global variable changed by a processor must be passed to other processors.
VSM is implemented through a programming model, where software creates and manages all of the communication between the processors and the memory. VSM is implemented on a distributed computing environment, but provides the connected processors with the impression that they are in a shared memory environment (a single memory shared between multiple processors). It is primarily implemented to provide a uniform value of the data being processed within the memory to all connected processors.
For example, if a processor is changing/altering the variable X, all other processors working on the same variable will see the new value.