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Appendix D 371
Using SNAplus2 in a High Availability Environment
Using SNAplus2 with MC/ServiceGuard
and become active. If this parameter is not specified, 10
retries will be allowed. Any number between 0 and 600
(inclusive) can be specified.
The return code of snapmon is 0 if the LS was active at some time while
snapmon was running. Otherwise, a non-zero value is returned.
One snapmon Service Command will be listed in the Package Control
Script for each SNAplus2 LS that should be monitored. For example, to
monitor an SNAplus2 LS called HALS, you might put the following line in
the Package Control Script:
SERVICE_CMD[0]=”/opt/sna/bin/snapmon -i1 -r60 HALS”
When ServiceGuard starts the SNAplus2 package, it will also start the
snapmon Service to monitor the package. The snapmon utility will
obtain the status of the HALS connection from SNAplus2 every second.
Snapmon will wait 60 seconds for th e LS to become active. If HALS fails
to become active within 60 seconds, or if it activates and then
deactivates, the snapmon process will terminate. The termination of the
process will signal ServiceGuard that the SNAplus2 package is no longer
providing SNA network connectivity, and the package should be
migrated to another server.
Once you have created the basic package, read this section to determine
how to customize your SNAplus2 package. You will need to modify the
SNAplus2 Package Control Script to complete your SNAplus2 package
definition.
Specifying a Package IP Address
An IP Address must be associated with the SNAplus2 package even if
you are not using a LAN (802.3, Token Ring, or FDDI) for SNA network
connectivity. This is a ServiceGuard requirement. This address is called
a “floating” IP address, because whenever ServiceGuard migrates a
package (or performs a local failover), the floating IP address moves with
the package. Since ServiceGuard moves the floating IP address with the
package, a ssociating an IP address with a package provide s a high
degree of availability when access to a particular LAN adapter has been
cut off .
ServiceGuard prevents TCP/IP connections from being disconnected
when a local LAN failover occurs. Although an IP address must be
associated with the SNAplus2 package, there are only limited uses for
this address in SNAplus2 networks. Users of SNAplus2 applications will
no t always be able to take advantage of ServiceGuard’s local failover