Managing HP Serviceguard A.11.20.20 for Linux, March 2014

4.8.7.2.1 Dragging Rules for Simple Dependencies
The priority parameter (page 179) gives you a way to influence the startup, failover, and failback
behavior of a set of failover packages that have a configured_node failover_policy,
when one or more of those packages depend on another or others.
The broad rule is that a higher-priority package can drag a lower-priority package, forcing it to
start on, or move to, a node that suits the higher-priority package.
NOTE: This applies only when the packages are automatically started (package switching
enabled); cmrunpkg will never force a package to halt.
Keep in mind that you do not have to set priority, even when one or more packages depend
on another. The default value, no_priority, may often result in the behavior you want. For
example, if pkg1 depends on pkg2, and priority is set to no_priority for both packages,
and other parameters such as node_name and auto_run are set as recommended in this section,
then pkg1 will normally follow pkg2 to wherever both can run, and this is the common-sense (and
may be the most desirable) outcome.
The following examples express the rules as they apply to two failover packages whose
failover_policy (page 178) is configured_node. Assume pkg1 depends on pkg2, that
node1, node2 and node3 are all specified (in some order) under node_name (page 176) in the
configuration file for each package, and that failback_policy (page 179) is set to automatic
for each package.
NOTE: Keep the following in mind when reading the examples that follow, and when actually
configuring priorities:
1. auto_run (page 176) should be set to yes for all the packages involved; the examples assume
that it is.
2. Priorities express a ranking order, so a lower number means a higher priority (10 is a higher
priority than 30).
HP recommends assigning values in increments of 20 so as to leave gaps in the sequence;
otherwise you may have to shuffle all the existing priorities when assigning priority to a new
package.
no_priority, the default, is treated as a lower priority than any numerical value.
3. All packages with no_priority are by definition of equal priority, and there is no other
way to assign equal priorities; a numerical priority must be unique within the cluster. See
“priority” (page 179) for more information.
4.8 Package Configuration Planning 115