This field records the state the application process was in immediately before its most recent state transition, per the description. Pairing this old-state value with the very next OID, cbsModuleAppNewState, lets an admin reconstruct exactly which transition occurred - for example distinguishing a clean 'active to stopped' shutdown from an unexpected 'active to faulted' crash - which a bare current-state snapshot alone could not show. Seeing this field read 'active' immediately before a new-state reading of 'faulted' would flag an abnormal crash rather than a planned stop.