Dynamically managed CHPIDs

A key aspect of the Intelligent Resource Director (IRD) provided by the WLM component of z/OS® is Dynamic CHPID Management (DCM). DCM provides the ability to have the system automatically move the available channel bandwidth to where it is most needed. CHPIDs identified as managed in the IOCDS (by using CHPARM and IOCLUSTER keywords) are dynamically shared among z/OS images within an LPAR cluster.

Before DCM, available channels had to be manually balanced across I/O devices in an attempt to provide sufficient paths to handle the average load on every controller. Natural variability in demand means that some controllers at times have more I/O paths available than they need, while other controllers possibly have too few. DCM attempts to balance responsiveness of the available channels maximizing the utilization of installed hardware. Fewer overall channels are required because the DCM CHPIDs are more fully used. RMF provides a report showing the average aggregate utilization for all managed channels.

By using DCM, you now only have to define a minimum of one nonmanaged path and up to seven managed paths to each control unit (although a realistic minimum of two nonmanaged paths are recommended), with dynamic channel path management taking responsibility for adding additional paths as required. For more information about defining and using DCM, including detailed examples, see the z/OS Intelligent Resource Director, SG24-5952.