This
section is relevant only if you installed SNAplus2 to run in a client/server
environment (with multiple SNAplus2 nodes in the same network).
Many resources, such as ports and LUs, are configured on an
individual node. These are known as “node resources.”
Other resources, such as emulator user definitions, are common
to all nodes; only one definition for the resource is maintained
for the entire domain. Such resources are known as “domain
resources.”
Domain resource definitions are stored only on the master server
for the domain, and are accessible from all the nodes in the domain.
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 | NOTE: A standalone SNAplus2 system has only one server; that
server always acts as the master. |
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In a client/server environment, a server can be marked as
a configuration server; SNAplus2 maintains a list of these
configuration servers. The first server listed is the master server,
and any other servers listed are backup servers.
The servers are listed in order, so that the second server listed
(the first backup server) takes over if the master server is unavailable,
the third server listed (the second backup server) takes over if
neither the master nor the first backup server is available, and
so on.
When any of the nodes in the domain are active, the first
available configuration server in the domain (the first server that
can be contacted and has SNAplus2 software running) becomes the
master server. If the current master becomes unavailable (because
it cannot be contacted, perhaps due to a network failure, or because
the SNA software running on it is stopped), the next available configuration
server in the list becomes the new master.
SNAplus2 can run without a master. This happens if none of
the servers in the configuration server list can be contacted. If
this happens, you can view and configure node resources only on
the servers that can be contacted.
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| NOTE: You cannot directly indicate which node acts as the
master server; the master server is selected based on the order
in which nodes are added to the configuration server list. If you
wish to move a server to the top of the list, remove all other nodes
from the list and then add them again. |
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In
the Motif administration program Domain window, you can add a configuration
server by selecting Make
configuration server from the Selection menu. The server is
added to the end of the list; it becomes the master server only
if all other configuration servers are unavailable. To remove a
server,
select Remove configuration
server from the Selection
menu.
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| NOTE: You cannot delete a server if it is the only server
listed on which the SNAplus2 software is running, because in this
case there is no other server that can take over as the master server.
At least one enabled master server is required in a client/server
configuration. |
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You can also use the
following administration commands to query, add, and delete configuration
servers:
- query_sna_net
Lists the servers in the file.
- add_backup
Adds a new server to the end of the list.
- delete_backup
Removes a server from the list. You can use the
delete_backup command to delete
either the master server (so that the second server listed takes
over as master) or a backup server (so that it can no longer act
as the master).
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