What is a work process in the SAP application server?

A work process is an individual unit within an SAP application server responsible for actually executing a piece of work — running an ABAP program, handling a database update, processing a background job, and so on. An application server runs a pool of these work processes, and a dispatcher assigns incoming user requests to an available one.

flowchart LR
    A[User request arrives] --> B[Dispatcher]
    B --> C[Available Work Process executes it]
    C --> D[Result returned to user]

Different work process types handle different kinds of tasks — dialog work processes handle interactive user requests, background work processes run scheduled batch jobs, update work processes handle database commits, and so on. Because there's a limited pool of work processes per application server, having too few relative to system load is a classic cause of users experiencing slow response times, since requests have to wait for a work process to free up.