The Question is:
Can a port allocation class for a SCSI adapter be set to the same value as the
system allocation class. Its not clear to me from the docs if allcoation class
and port allocation class are globally unique or only need to be uniqe within
each class. E.g.
Can I set ALLOCLASS = 1, PORT allocation class for PKA to 1 and Port allocation
class for PKB to 51.
The Answer is :
The OpenVMS Wizard would recommend that the host remain in allocation
class zero, or that the host be configured in a unique and non-zero
allocation class. The OpenVMS Wizard would not generally recommend
configuring any cluster host and any port in the same allocation class.
The allocation class mechanism is intended to provide a way to avoid
device unit number collisions. Each disk and each tape device in any
particular (non-zero) disk and tape allocation class -- host or port
or storage controller -- must have a unique device unit number, across
all cluster members.
Any device that is served via multiple hosts (via OpenVMS and a shared
bus, or via a storage controller) should be configured in the same
non-zero allocation class.
Devices in allocation class zero are assumed to be host-local, are
identified by the host name, and the unit numbers -- which must be
unique on the local host -- can potentially overlap across hosts.
Also please see the OpenVMS FAQ section on configuring allocation
classes and Multi-Path SCSI, and the section on OpenVMS host-based
volume shadowing (mirroring) and (non-zero) allocation classes.