User's Guide

templates, SAP software service monitors as well as specialized additional features to integrate hot standby
liveCache scenarios, HP Workload Management scenarios and HP Event Monitors.
There are three major Serviceguard modules delivered with SGeSAP. For the standard SAP Netweaver web
application server stack it provides a Serviceguard module called sgesap/sapinstance. This module
can be used to easily add a set of SAP instances that belong to the same Netweaver-based system to a
module-based Serviceguard package. The package can encapsulate the failover entity for a combination
of ABAP-stack, JAVA-stack and dual-stack instances plus, optionally, either Central Service Instances or
Enqueue Replication Service Instances of an SAP System. For MAXDB or Oracle-based SAP database services,
the module sgesap/dbinstance can be used. The module to cluster SAP liveCache instances is called
sgesap/livecache. In addition to these three major modules, there are two more modules that enable
easy clustering of smaller SAP infrastructure software tools sgesap/sapinfra and allow to manipulate
the behavior of non-clustered SAP instances sgesap/sapextinstance. The covered infrastructure tools
include the SAP sapccmsr, saposcol, rfcadapter and saprouter binaries. Other SGeSAP module
names exist that provide a combination or subset of the functionality of some of the five modules mentioned
above. They were primarily defined for convenience reasons to simplify configuration steps for standard use
cases.
In legacy packaging each software Single Point of Failure defines a SGeSAP package type. SGeSAP follows
a consistent naming convention for these package types. The naming conventions were created to be
independent of SAP software release versions. This allows to use a similar approach for each SPOF, regardless
of whether it appears in the latest SAP Netweaver stack or a SAP software that was released before the first
design of SAP Application Server. Older SAP components sometimes only support a subset of the available
clustering options.
Defining a mixture of legacy packages and module-based packages is possible in the same cluster. MDM
packages, cross-subnet extensions for non-production use and SAP dispatcher monitoring are currently
available in legacy packages only. Legacy-based packages will be discontinued at a later point in time. By
then, all SGeSAP functionality will be available in a module version.
Table 1-1 Mapping the SGeSAP legacy package types to SGeSAP modules and different SAP naming
conventions
Commonly used SAP instance namesSGeSAP module namesSGeSAP legacy package type
DVEBMGS (as Central Instance), ASCSsgesap/sapinstance
alternatives: sgesap/scs
sgesap/ci
ci
SCSjci
AREP, ENR, ERSsgesap/sapinstance
alternatives: sgesap/ers
arep
REP, ENR, ERSrep
D, DVEBMGS (new)sgesap/sapinstanced
JDI, JD, JC, Jjd
sgesap/dbinstance
alternatives:sgesap/db
sgesap/maxdb sgesap/oracledb
db
sgesap/livecachelc
Mutual Failover Scenarios Using the Two Package Concept
Most SAP applications rely on two central software services that define the major software Single Point of
Failure (SPOF) for SAP environments: the SAP Enqueue Service and the SAP Message Service. These services
are traditionally combined and run as part of a unique SAP Instance that is referred to as JAVA System
Central Service Instance (SCS) for SAP JAVA applications or ABAP System Central Service Instance (ASCS)
for SAP ABAP applications. If an SAP application has both JAVA and ABAP components, it is possible to
have both - an SCS and an ASCS instance - for one SAP application. In this case, both instances are SPOFs
that require clustering.
In pure ABAP environments, the term Central Instance (ci) is still in use for a software entity that combines
further SAP application services with these SPOFs in a single instance. As any other SAP instance, a Central
Instance has an Instance Name. Traditionally it is called DVEBMGS. Each letter represents a service that is
delivered by the instance. The "E" and the "M" stand for the Enqueue and Message Service that were
12 Designing SGeSAP Cluster Scenarios