HP-UX SNAplus2 R7 Administration Guide
Introduction to SNAplus2
SNAplus2 Components
Each server maintains information about its own node configuration in a node configuration file. You can use the
SNAplus2 administration tools, described in Section 3.1.2,
Administration Tools, to examine and modify the node’s
configuration. You can configure a node from any other computer in the domain, as long as the SNA software is
running on the node where the configuration is performed (whether or not the node being configured is started).
Information about the configuration of domain resources for the complete SNAplus2 LAN is held in a domain
configuration file. If you have more than one server on the LAN, SNAplus2 ensures that this domain configuration
information is consistent across all servers.
Benefits of Client/Server Operation
Client/server configuration provides the following benefits:
• Concentrating SNA resources on servers reduces the load on clients, improving client performance and
minimizing the storage needed to provide SNA services to clients.
• Sharing a single data link among multiple users on different machines eliminates the need for each machine to
have a physical SNA network connection.
• Having multiple servers provides redundant connectivity (for example, by having multiple servers providing
access to the same host). Having multiple paths to an SNA resource enables load balancing across the different
servers and provides immediate backup in the event that a particular server or link fails.
• Using LU pools across multiple servers makes it easy to configure and add servers and users.
• Having fewer links and PUs for host connectivity reduces the size of the host VTAM definition.
• Using SNAplus2 administration utilities makes it easy to configure and manage both node resources (for any
specific computer in the domain) and shared resources (across the domain). The client/server support provided
by SNAplus2 administration tools enables transparent administration of all domain resources from any computer
in the domain.
Master Server and Backup Servers
If you are using SNAplus2 with all programs on one computer, or on a LAN that contains only one server, you do
not need to read this section.
In a domain with multiple SNAplus2 servers, one server holds the master copy of the SNAplus2 domain config-
uration file. This server is known as the master server. You can define other servers in the domain to be backup
servers. The domain configuration file is copied to backup servers—either when they are started, or when the mas-
ter copy is changed—so that all backup servers hold a copy of the latest information.
In general, you should define at least one backup server in addition to the master server. Any remaining servers
can be defined as additional backup servers, or they can be left as peer servers. A peer server obtains domain
configuration information from the master server as required, but cannot act as a backup server.
If the master server fails, the first backup server on the list of servers defined for the domain takes over as the
master. The domain configuration file on this server is used as the master copy, and is copied to other servers as
necessary. When the master server is restarted, it receives a copy of the domain configuration from the backup
server currently acting as master, and then takes over as the master.
If at any time the master server and all backup servers are inactive, a node on a peer server can still operate,
and you can still change the node’s configuration. However, you cannot access the domain configuration file, and
therefore cannot access the configuration of domain resources (as opposed to node resources). This means that you
cannot start the 3270 emulation program, start the RJE programs, or allocate CPI-C conversations using symbolic
destination names defined in the configuration file.
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