You can use Hitachi Dynamic Link Manager (HDLM) to specify preferred paths to be used for normal global-active device operations by using host mode options (HMOs).
Other paths are used when failures occur in the paths that should be used for normal operations. HMO 78, the nonpreferred path option, must be configured to specify nonpreferred paths, which are used when failures occur.
For example, if servers and storage systems are connected in a cross-path configuration, I/O response is prolonged because the primary-site server is distant from the secondary storage system, and the secondary-site server is distant from the primary storage system. Normally in this case you use paths between the primary server and primary storage system and paths between the secondary server and secondary storage system. If a failure occurs in a path used in normal circumstances, you will use the paths between the primary server and secondary storage system, and paths between the secondary server and primary storage system.
When the settings are applied to HDLM, the attribute of the HDLM path to which HMO 78 was set changes to non-owner path. The attribute of the HDLM path to which HMO 78 was not set changes to owner path. For details, see the HDLM documentation.