Dynamic configuration of channel-attached devices

Dynamic configuration of channel-attached devices (dynamic I/O) enables you to modify your I/O configuration without disrupting your system. You can add, delete, or modify I/O components, such as devices and paths, without having to re-IML or re-IPL.

Use the following items to dynamically configure your channel-attached devices and dynamically create VTAMLST members for new devices:
  • Hardware configuration definition (HCD)
  • NetView® Release 3 and subsequent releases, or a product with a similar interface and services
Note: NetView and TSO/E are necessary for dynamically creating VTAM®LST members using the VTAM-supplied sample command lists. To modify the I/O configuration only, you need only MVS™ and HCD.

Figure 1 shows how a channel-attached device is added using dynamic I/O configuration support.

  1. Physically attach a device.
  2. Add the device to your configuration using hardware configuration definition (HCD), and activate the new configuration using the MVS ACTIVATE command.
  3. MVS issues message IOS502I, which causes NetView to start the IOS502I command list.
  4. The IOS502I command list calls the ISTDEFIN command list for each device added to the system.
  5. The ISTDEFIN command list obtains a description of the new device using the ISTDINFO function module, which obtains the new device information and returns it to ISTDEFIN.
  6. The ISTDEFIN command list builds a VTAMLST member for the device. Any information the device cannot provide can be found with IBM®- or user-supplied defaults.
  7. The ISTDEFIN command list issues a VARY ONLINE command for the device if it is not already online.
  8. The ISTDEFIN command list issues a VARY ACT command to activate the device.
Figure 1. Dynamic configuration of channel-attached device
Diagram that shows how a channel-attached device is added by using dynamic I/O configuration support.