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.