Defining LUN 0 on OpenVMS

In the system, LUN 0, which is needed for all LUNs recognition, is represented as a regular disk on OpenVMS hosts. LUN 0 must be attached to the host at all times.

In the system and in other storage products, LUN 0 is used as the Command Console LUN (CCL), or pass-through LUN.

Note: System notification messages might appear on a host as ASC/ASCQ errors, such as x2500 (Logical Unit Not Supported), x2900 (POWER ON, RESET, OR BUS DEVICE RESET OCCURRED), and x3F0E (Direct Access Device ASC/ASCQ unrecognized). These errors do not result in any data or access loss.

OpenVMS hosts require volumes with SCSI LUN 0 to be mapped. This action enables an OpenVMS host to recognize any other volumes that are mapped to the host. By default, the lowest available SCSI LUN ID is used when mapping a volume to a host.

The returned ID is the same for all I/O groups to which the volume is mapped. If an identical SCSI LUN ID is not available in all of the access I/O groups, the command fails. Use the -allowmismatchedscsiids parameter to allow the system to allocate non-identical SCSI LUN IDs in the access I/O groups. The lowest value available in each access I/O group is used. It might not be the same in all access I/O groups. Make sure that the host supports this configuration. This parameter cannot be used with the -scsi parameter.

You can set the SCSI LUN ID manually when creating a mapping by using the -scsi parameter. The following example creates a mapping with SCSI LUN ID 0:

mkvdiskhostmap -host host_name|host_id -scsi 0 vdisk_name|vdisk_id