How to configure allocation classes and Multi-Path SCSI?
The HSZ allocation class is applied to devices, starting with OpenVMS V7.2. It is considered a port allocation class (PAC), and all device names with a PAC have their controller letter forced to “A”. (You might infer from the the text in the “Guidelines for OpenVMS Cluster Configurations” that this is something you have to do, though OpenVMS will thoughtfully handle this renaming for you.) You can force the device names back to DKB by setting the HSZ allocation class to zero, and setting the PKB PAC to -1. This will use the host allocation class, and will leave the controller letter alone (that is, the DK controller letter will be the same as the SCSI port (PK) controller). Note that this won’t work if the HSZ is configured in multibus failover mode. In this case, OpenVMS requires that you use an allocation class for the HSZ. When your configuration gets even moderately complex, you must pay careful attention to how you assign the three kinds of allocation class: node, port and HSZ/HSJ
