HP-UX SNAplus2 R7 Administration Guide

Appendix DUsing SNAplus2 in a High Availability Environment
AppendixD Using SNAplus2 in a High
Availability Environment
This appendix describes the high availability features of SNAplus2 and how it works with the HP MC/ServiceGuard
product.
D.1 What is High Availability?
High availability is a term used to describe an environment in which mission critical applications are protected from
severe impact of various failures. These failures might include entire computer system failures, network failures,
software failures, power failures, disk drive failures, and I/O interface failures. If the result of any one failure is
the complete loss of the mission critical application, then a
single point of failure exists. The main goal of high
availability is to achieve maximum uptime. High availability networks should have sufficient redundancy of software
and hardware components so that a single point of failure will not disrupt service.
To see what types of failures are considered important, look at the following example of a typical SNAplus2 client/
server network that is not designed for high availability.
Figure D–1 SNAplus2 client/server network
Client Client Client
3xxx
Communications
Controller
S800
Server
IBM
Host
LAN
Client/server network link
SNAplus2 Link software
SNA network link
Disk Drives
Client
In this environment, applications run on client systems (HP9000s or PCs) and access the IBM mainframe through an
HP9000 S800 server. The application might be SNAplus2 3270 or a custom application like an APPC transaction
205