Hardware Configuration Definition (HCD)

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You can use HCD in z/OS® or z/VM® to define configuration information both to the CPC and to the operating system. In z/OS, you can use the interactive panels of HCD or Hardware Configuration Manager (HCM) for definition; in z/VM, use HCM.

HCD allows you to dynamically change the current I/O configuration of the CPC. HCD allows you to dynamically change the current I/O configuration of the operating system and to create an IOCDS and make it the active IOCDS.

In z/OS, HCD is required to define the I/O configuration to the operating system. HCD is also the recommended way to define hardware configurations. HCD must be used, if the I/O configuration is dynamically changed in z/OS.

In z/VM, HCD is optional for defining the I/O configuration. If HCD is used for dynamic changes, the hardware configuration must be defined with HCD, the I/O configuration for the operating system may be defined with HCD.

HCD allows you to define the hardware and software I/O configuration information necessary for a parallel sysplex solution environment, including the capability to define:

  • peer-mode channel paths (CE LR, ICA SR coupling links, and ICP) to connect z/OS systems to coupling facility images, and
  • peer-mode channel paths (CE LR, ICA SR coupling links, and ICP) to connect coupling facility images to one another, in support of System-Managed CF Structure Duplexing.

In addition to these two uses, the external coupling links (CE LR, ICA SR coupling links) also support STP timing signals.

Additionally, HCD in z/OS allows you to remotely write IOCDSs from one Support Element to another Support Element as long as both Support Elements are powered-on, LAN-attached, enabled for remote licensed internal code (LIC) update, and defined to the same Hardware Management Console.

Dynamic I/O configuration does not support:

  • Changing MIF image ID numbers (the MIF image ID number is different from the LP identifier [ID])

When using HCD, you can define and control the configuration of the CPC affecting all LPs. Those LPs that run with HCD or z/VM can dynamically change their software configuration definitions. Other LPs might require an IPL in order to use the new configuration.

HCD allows you to discover and automatically define switched FICON® attached storage control units and devices.

When you use HCD you must install, in the LP, the appropriate version of IOCP. Throughout the remainder of this publication, all the capabilities or restrictions documented regarding the IOCP program, also apply to definitions entered and controlled through HCD.

For more information about dynamic I/O configuration on z/OS, see:

  • z/OS Hardware Configuration Definition Planning, GA32-0907
  • z/OS Hardware Configuration Definition User's Guide, SC34-2669

For more information about dynamic I/O configuration on z/VM, see:

  • z/VM I/O Configuration, SC24-6291