Abstract: A computer system and method restart only affected system program code levels of a computer system in response to a program code update to one or more system program code levels in the computer system. An affected system program code level may be a system program code level that is modified by a program code update, as well as a system program code level that otherwise must be restarted in response to an update to another system program code level. By restarting only affected system program code levels in response to a program code update, the time required to perform many program code updates may be reduced. As a result, the downtime for the computer system may be minimized, thereby maximizing user access to enterprise-critical computer systems.

Abstract: A monitor circuit for overseeing input/output activity in a digital computing system is disclosed. The circuit comprises a memory array for storing subchannel status words, each of which corresponds to an input/output operation unit. Each subchannel status word includes a timing monitor field having a current count subfield, a count limit subfield, and a command-in-progress bit position. Circuits are provided for incrementing at timed intervals numbers encoded in the current count subfields of those subchannel status words against which a request for an input/output operation is outstanding. A circuit is provided for comparing the numbers encoded in the current count subfields to the count limit subfields to determine if a response to a request for an input/output operation is overdue.