This read-only integer reports the current number of bytes in this process's Working Set, the set of memory pages its threads have touched recently, which stays resident even when unused if free memory is plentiful but gets trimmed when memory is scarce. An admin watches this to see how much physical memory a specific process is actively holding. For example, a process's cpqOsProcessWorkingSet shrinking sharply under memory pressure and then generating soft page faults afterward reflects the OS trimming and later re-faulting its pages.