Managing Serviceguard Extension for SAP, December 2007

Understanding Serviceguard Extension for SAP
Designing SGeSAP Cluster Scenarios
Chapter 120
Robust Failover Using the One Package Concept
In a one-package configuration, both the database (db) and Central
Instance (ci) run on the same node at all times and are configured in one
SGeSAP package. Other nodes in the Serviceguard cluster function as
failover nodes for the primary node on which the system runs during
normal operation.
NOTE The naming convention for these packages are dbciSID.
It is a good practice to keep a cluster setup as simple as possible. Less
packages need less system resources and can easily be monitored. If
database and Central Instance get combined in a single package, this can
safe administration overhead.
It is not required to maintain an expensive idle standby. SGeSAP allows
to utilize the secondary node(s) with different instances during normal
operation. A common setup installs one or more non-mission critical SAP
Systems on the failover nodes, typically SAP Consolidation, Quality
Assurance or Development Systems. They can gracefully be shutdown by
SGeSAP during failover to free up the computing resources for the
critical production system.
Development environments tend to be less stable than production
systems. This should be taken into consideration before mixing these
use-cases in a single cluster. A feasible alternative would be to install
Dialog Instances of the production system on the failover node.
If the primary node fails, the database and the Central Instance fail over
and continue functioning on an adoptive node. After failover, the system
runs without any manual intervention needed. All redundant
Application Servers and Dialog Instances, even those that are not part of
the cluster, can either stay up or be restarted triggered by a failover.