Automatic channel path reconfiguration

PR/SM records shared channel path configurations and unshared channel path reconfigurations and uses the information to modify the initial targeting of channel paths that are defined in the IOCDS. This information is maintained on an IOCDS basis.

When a particular IOCDS is used in a POR for the first time after it has been written, the definitions in that IOCDS are used to determine the assignment of channel paths to LPs according to the channel path access lists that are defined. All previous information about channel configuration associated with this IOCDS is discarded. The exception to this rule is when a newly written IOCDS is first used as part of a dynamic I/O change to the system. (For example, the new IOCDS is used as a result of a "Switch IOCDS for Next POR" action by HCD, or the new IOCDS is the target of the ACTIOCDS= parameter of the z/OS® ACTIVATE command.) When a new IOCDS is used in this manner, the current state of channel configurations is preserved and immediately associated with the newly written IOCDS.

Over time, the list of channel paths targeted to be configured online to a given LP can be changed by system control program configuration commands, configure on tasks, or dynamic I/O configuration commands issued through HCD or z/VM®. Similarly, reconfigurable unshared channel paths can be moved from one LP to another using the same commands; changing the owner of the unshared channel path. For activated coupling facility LPs, you can change the channel paths targeted to be configured online using coupling facility control code commands. Automatic channel path reconfiguration restores all of the latest changes for each POR with the IOCDS automatically.

Automatic channel path reconfiguration does not preserve the online/offline state of unshared channel paths (reconfigurable or dedicated). Rather, at POR time, all unshared channel paths are targeted to come online to the LP that last owned it. For dedicated channel paths, this owner never changes but for reconfigurable channel paths the owner can change and is remembered.

Following a POR, a channel path that is targeted to come online to a LP will be physically online to that LP and usable at the completion of activation for the LP.