Managing Serviceguard Extension for SAP, December 2007

Understanding Serviceguard Extension for SAP
Dialog Instance Clusters as Simple Tool for Adaptive Enterprises
Chapter 126
Dialog Instance Clusters as Simple Tool for
Adaptive Enterprises
Databases and Central Instances are Single Points of Failure. ABAP and
JAVA Dialog Instances can be installed in a redundant fashion. In
theory, this allows to avoid additional SPOFs in Dialog Instances. This
doesn’t mean that it is impossible to configure the systems including
SPOFs on Dialog Instances. A simple example for the need of a SAP
Application Server package is to protect dedicated batch servers against
hardware failures.
SAP ABAP Dialog Instances can be packages using package type ‘d’. SAP
JAVA Dialog Instances can be packaged using package type 'jd'. Instance
packages differ from other packages in that there might be several of
them for one SAP SID. Therefor the naming convention is slightly altered
and the unique Instance Number of the Application Server is added. A
Dialog Instance package for Instance Number 01 of SAP System SID
would be called d01SID or jd01SID.
As with any other SAP component, Dialog Instances can now freely be
added to packages that also protect other parts of the setup. It is
suggested to only apply the Dialog Instance naming convention if there
are no mission-critical core components in the package. In other words,
adding a Dialog Server to a dbciSID package should not change the
package name.
NOTE Most SAP software components for a specific SAP application can only be
specified once in a cluster. Likewise they can also only be specified once
within a single package. Dialog Instances make an exception in that
there can be an array of these clustered by a single package. There can
also be multiple packages with Dialog Instances.