What is an I/O Configuration?

Your processor's I/O configuration is comprised of the:
  • Channel paths on your processor complex
  • Control units attached to the channel paths
  • I/O devices assigned to the control units.
  • Logical partitions

In the processor, the channel subsystem (CSS) uses information about your I/O configuration to direct the flow of information between I/O devices and main storage, relieves the processor of communication tasks, and performs path management functions.

Once your z/VM® system is up and running, there will be occasions where you want to change your I/O configuration. On a z/VM system that does not support dynamically changing the I/O configuration (that is, before VM/ESA® Version 2 Release 1.0), you would have to perform the following steps for your I/O configuration changes to take effect:

  1. Update the I/O configuration program (IOCP) source file,
  2. Download the I/O configuration to the support element (SE) using the IOCP utility,
  3. Shutdown z/VM (the operating system),
  4. Perform a power-on reset (POR) of the hardware, and
  5. Perform an initial program load (IPL) of the software

Note: If your processor is in logically partitioned (LPAR) mode and one of the logical partitions is running z/OS, you can dynamically change the I/O configuration using the Hardware Configuration Definition* (HCD*) component. However, you cannot use the z/VM and z/OS dynamic I/O configuration facilities simultaneously. You must decide whether z/VM or z/OS will be dynamically changing the I/O configuration.