The second line of the channel block specifies the official host name associated with the channel along with an optional alias for the local host. The line has the form:
official-host-name, should be the full name (including any subdomains or domains) of the host with which the channel communicates. In the case of the local channel, the name should be the preferred name used locally for the host PMDF is running on. In a homogeneous OpenVMS cluster environment this name will apply to the entire cluster; it does not have to be a name associated with any particular cluster node. All official host names for all channels are stored in a single common lookup table. They must be unique; duplicates are not allowed.
The local host machine is normally known by the name that appears as the official host name in the first channel block (on OpenVMS and UNIX, the l channel --- note that this is a lowercase letter "L"; on NT normally a msgstore channel) in the configuration file. It is sometimes useful for the local host to have different names depending on the channel being used. This situation usually arises when a machine is connected to more than one network. For example, a system may need to be known as milan.uucp on the UUCP network, milan.example.com on the Internet, and milan.bitnet on BITNET.
The local host alias,
local-host-alias, on the
second line of the channel block provides this functionality. If this
alias is specified, it is communicated as the local host's name to any
remote hosts with which this channel communicates. This alias will
replace the local host's name wherever it appears in the envelope and
header of messages queued to the associated channel. If this alias is
omitted the local host's official name (that is, the official host name
associated with the l channel) is used.
The local host alias only affects the name of the local host. No other system names are affected. The effects of the local host alias are strictly limited to the channel to which the alias applies.
The use of local host aliases is discouraged. If at all possible, each system should be known by one and only one name on all networks. Networks should strive to make this a reality. The current Internet versus UUCP versus BITNET networking fracas leads to situations where this feature is needed. In particular, it is presently impossible for a host on both BITNET and the Internet to have exactly the same name on both networks. Since different networks are associated with different channels, a per-channel local host alias is an ideal way to give the local host a per-network name.
When a single network is involved, it may appear that local host aliases can solve lots of problems, but often the end result is a worse mess than if the proper course of action is selected --- pick a single name and stick to it, living with the consequences of the conversion now instead of putting them off until it becomes even more difficult.