High Availability Monitors Version A.03.02 Release Notes

Introduction to the NOF API

Client-Server Operation

Chapter 1 63

Client-Server Operation

The computers on the SNAplus2 LAN are of two types: servers and

clients. A server contains a SNAplus2 node and its associated

connectivity components; a client does not contain these connectivity

components, but accesses them on the server by means of the LAN.

Servers must be HP-UX computers; clients may be running HP-UX or

Windows systems. Servers and clients communicate across the LAN

using Berkeley Software Distribution (BSD) Sockets.

Each SNAplus2 LAN system, referred to as a domain, is identiﬁed by a

domain name. This name is speciﬁed during the installation of each

SNAplus2 computer (server or client), so that all computers in a single

SNAplus2 LAN system have the same domain name. To install two

separate SNAplus2 domains on the same physical network, you simply

use two different domain names to identify which domain each computer

belongs. A single SNAplus2 domain can correspond to a TCP/IP subnet,

can be part of a TCP/IP subnet (so that there are two or more separate

SNAplus2 domains in the same subnet), or can span multiple subnets.

Each server maintains information about its own node conﬁguration in a

node conﬁguration ﬁle. You can use the SNAplus2 administration tools

or the NOF API to examine and modify the node's conﬁguration. This

can be done either from this server or from any other computer in the

domain, as long as the SNA software is running (whether or not the node

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 information is

consistent across all servers.

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.

At any time, one server on the LAN, known as the master server, holds

the master copy of the SNAplus2 domain conﬁguration ﬁle. You can

deﬁne other servers on the LAN to be backup servers; the domain

conﬁguration ﬁle is copied to backup servers (either when they are

started or when the master copy is changed) so that all backup servers