HP-UX SNAplus2 R7 Administration Guide

Appendix DUsing SNAplus2 in a High Availability Environment
D.4 Advanced Configuration Techniques
The following advanced configuration techniques are useful in networks where there are multiple DLC (Data Link
Control) types connecting one or more HP 9000 servers to the remote SNA system. For example, a standalone
server might use a Token Ring LAN to communicate with the remote system, but have an SDLC DLC ready to use
if the token ring is unavailable.
Figure D–16 Standalone Server using Token Ring Primary DLC and SDLC Backup DLC
3xxx
Communications
Controller
IBM
Host
HP 9000
Server
Backup DLC
Primary DLC
SDLC
Token
Ring LAN
The idea is that when SNA networking problems occur, simply switching to a different link type on the same HP
9000 server often restores network connectivity without having to perform a remote failover.
Previously, we discussed how to use snapmon as a Service in the Package Control Script to monitor an SNAplus2
LS and inform ServiceGuard of a failure. In the following sections we will explain how to add more intelligence to
the Service in the Package Control Script that will allow you to attempt local recovery before informing ServiceGuard
that a remote failover is necessary.
D.4.1 Writing Your Own SNAplus2 Service Script
By customizing the Service used in the Package Control Script, you can do the following:
• Automatically attempt local restart of an SNAplus2 package that has failed.
• Automatically attempt local failover to another network adapter when one fails.
• Use a backup link type when the primary link fails.
Local failover allows SNAplus2 to attempt local recovery of an SNAplus2 LS before informing ServiceGuard that
the package has failed. This will add more redundancy to your network and reduce even further the effects of a
single point of failure.
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