This section contains the following information to help you
plan for using DECdtm in a DECnet-Plus network:
Planning your
DECnet-Plus namespace
Planning SCSNODE names in
your DECnet-Plus network
Planning
Your DECnet-Plus Namespace DECdtm does not support multiple DECnet-Plus namespaces.
This means that if you want to use software that uses DECdtm
services, you cannot use both a local namespace and a DECdns namespace.
Planning
SCSNODE Names in Your DECnet-Plus Network SCSNODE is a system parameter that defines the name of the
computer. You must follow certain rules when choosing SCSNODE names
if you have a DECnet-Plus network and you want to perform DECdtm transactions
that span either different OpenVMS Clusters or different standalone
computers.
Rules for SCSNODE Names If you have a DECnet-Plus network and want to perform DECdtm
transactions that span different OpenVMS Clusters or different standalone
computers, you must make sure that your SCSNODE names obey the following
rules:
The SCSNODE
name of each computer in a transaction group must be different from:
The
SCSNODE names of the other computers in the transaction group; SCSNODE
names must be unique within a transaction group
The DECnet simple names of
other computers on the same local root
The DECnet synonyms of the
other computers in the entire network
If a computer is in an OpenVMS
Cluster, its SCSNODE name must also be different from:
The
DECnet simple name of the other computers in the same cluster
The DECnet simple names of
computers on the same local root as other cluster members
ACMS users, possibly Rdb users, and any other users
running a user-written application that calls DECdtm to participate
in a distributed transaction with a remote system that has the HP DECnet-Plus
for OpenVMS network connection and whose nodes are connected using
only an IP router might see the following error returned by DECnet:
IPC-E-BCKTRNSFAIL, failure on the back translate address request
This error is displayed upon a logical connection failure
when DECnet-Plus cannot translate the remote node name. The error
can be triggered when:
The
DECnet-Plus node name for the remote system is not defined in the
local DECnet-Plus database and is defined only as ALIAS in the TCP/IP
name server for the remote node. For example, node XXYZZY might be defined as follows:
20.43.136.54 XXYZZY.ABC.DEF.COM, XXYZZY
The node name cannot be resolved
from the DECnet database. In this case, the address resolution mechanism
will fall back on the TCP/IP database. If the node name is still
not resolved, the service might fail with the error cited above. To avoid this situation, register the SCSNAME in the
TCP/IP database.
Understanding
Transaction Groups A transaction group is a group of computers
involved in DECdtm transactions whose SCSNODE names must obey the
rules described in
Rules for SCSNODE Names.
A transaction group conforms to the following guidelines:
Each computer
belongs to no more than one transaction group.
All the computers in an OpenVMS
Cluster belong to the same transaction group.
If a single transaction spans
computers A and B, then computers A and B belong to the same transaction group.
All nine computers shown in the figure are in the same transaction
group because:
A transaction spans a computer in
cluster FRED and a computer in cluster BILL. This means that the four
computers in cluster FRED and the four computers in cluster BILL
are in the same transaction group.
A transaction spans standalone computer TOM and
a computer in cluster BILL. This means that the standalone computer
TOM is in the same transaction group as the computers in cluster
BILL.
HP OpenVMS System Manager's Manual, Volume 2:... 
Managing DECdtm Services
