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In a high availability system, every instance, such as the following instances, can run on a
separate host:
► Central services instance for ABAP (ABAP SAP Central Services (ASCS) instance)
► Enqueue replication server instance for the ASCS instance
► Database instance
► Central instance
The central services run in one z/OS logical partition (LPAR). Optionally, the enqueue
replication server runs in the second LPAR to provide failover capability. By using the DB2
data sharing feature, you can add System z servers to a sysplex, increasing the capacity of
the database server and enabling a sysplex failover. The considerations and performance
advantages mentioned also apply to this type of configuration.
Run the DB2 database server in data sharing mode. DB2 in data sharing mode is a true
parallel database server. With this setup, multiple DB2 subsystems share SAP database.
Each subsystem is called a data sharing member, and the set of subsystems is referred to as
a data sharing group. All members of the group use the same shared DB2 catalog and
directory, which guarantees redundancy of the database at the highest level. Additionally,
online backup and online recovery features, coupled with the features of System z platform,
provide high availability, DB2 rolling maintenance, and a release upgrade.
Attention: If availability of the entire SAP system is critical, see Business Continuity for
SAP on IBM System z, SC33-8206-04. For additional information, see the SAP on IBM
System z website at:
http://www.ibm.com/servers/eserver/zseries/software/sap
Table 6-1 outlines the tasks that are necessary to plan for and implement a high availability
solution for SAP.
Table 6-1 Planning and implementing an HA solution
Tasks for planning and implementing a HA solution HA at what level
Use DB2 on System z in data sharing mode. Database server
Configure the network between the application servers and
database server to be highly available. This configuration can be h
hardware-based or software based, by using such features as
z/OS VIPA.
Network
Install an SAP ASCS instance. SAP
Install an SAP enqueue replication server instance. SAP
Set up DB2 connection failover. SAP or database
Configure SAP logon groups. SAP
Automate system operations for SAP. This step includes
automating the start, stop, restart, and failover of SAP components
and all required z/OS components.
106 Running SAP Solutions with IBM DB2 10 for z/OS on the IBM zEnterprise System
OS