Input/Output Configuration Program: Difference between revisions

Revision as of 07:11, 31 August 2010

Revision as of 19:17, 31 August 2010

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| operating system = stand alone, z/OS, z/VM, z/VSE

| platform = [[IBM System/370#Expanding the address space|IBM System/370-Extended Architecture]]

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In the original [[IBM System/360|S/360]] and [[IBM System/370|S/370]] architectures, each processor had its own set of I/O channels and I/O device were addresses with a 12-bit ''cuu'' address, containing a 4-bit channel number and an 8-bit unit (device) number to be sent on the channel bus in order to select the device; the operating system had to be configured to reflect whatthe devicesprocessor wereand connected''cuu'' toaddress whatfor channelseach device. Initiating an I/O to a channel on a different processor required causing a [[shoulder tap]] to interrupt iton the other processor so that it could initiate the I/O.

Starting with the [[IBM 3081]] and [[IBM 4381]] in [[S/370 Extended Architecture]] mode, IBM introduced software configurable [[Channel Subsystem]]s, and allowed the operator to select an [[Input/Output Configuration Data Set]] (IOCDS) as part of of a [[Power On Reset]] (POR). Input/Output Configuration Program (IOCP)<ref name=GC38-0401/><ref name=GC38-0456/> is a program for IBM mainframes that compiles a description of the [[Channel Subsystem]] and [[LPAR]] configuration, optionally loading it into an [[Input/Output Configuration Data Set]] (IOCDS); it recognizes the syntax of [[MVS Configuration Program]] (MVSCP)<ref name=GC28-1615/> input, and there is no need to maintain separate input files.