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2.7.3 DB2 data sharing and GDPS
The objective of DB2 data sharing in a Parallel Sysplex environment is to keep the SAP
business applications available even if a single database member needs to be stopped.
If a connection is lost to the DB2 server, an SAP NetWeaver AS instantly reconnects to
another DB2 member in the same data sharing group. This way, SAP workloads can be
moved smoothly without being affected by these kinds of failures.
With the help of IBM Geographically Dispersed Parallel Sysplex (IBM GDPS®) on top of the
IBM System z Parallel Sysplex, you can apply this mechanism to geographically distributed
environments (connected over large distances). GDPS technology is also used to integrate
and ensure disaster recovery in such distributed environments.
If a local disaster occurs, disk IBM HyperSwap® technology ensures that systems
automatically swap to a synchronously mirrored site.
2.7.4 IBM System z Coupling Facility
The IBM System Coupling Facility that is used for the lock and shared communications area
(SCA) structures of the DB2 data sharing group must be failure isolated from the z/OS
systems that serve the data sharing group. The SCA is a list structure in the coupling facility.
2.8 Network setup
2.9 I/O setup
2.9.1 Metro Mirror
To ensure high-availability of the network, use static z/OS VIPAs for each LPAR running on a
DB2 member. This setup allows the SAP components to re-establish their connections to the
moved and restarted services by attempting to reconnect to the same VIPA.
This section highlights two technologies that differ in disaster resilience and are available for
storage subsystems. With the Metro Mirror and Metro/Global Mirror Copy Services features,
you can set up a relationship between two volumes, so that updates that are made by an
application to one volume are mirrored on the other volume. The volumes can be in the same
system or on two different systems.
With Metro Mirror technology (shown in Figure 2-7 on page 22), application failover occurs
across multiple servers. The GDPS/Peer-to-Peer Remote Copy (PPRC) HyperSwap Manager
controls the data replication in a single sysplex within a data center or simplifies replication
between two sites that are within the supported distance.
If a storage or subsystem failure occurs, with the GDPS HyperSwap Manager, seamless
takeover occurs within a few seconds. Within the process of swapping to another location, all
application and system-relevant data is included and consistently maintained.
With the DS8000 Remote Pair FlashCopy®, you can permanently mirror data to create DB2
backups and to allow GDPS to start HyperSwap when necessary so that all volumes are in
full duplex mode and network traffic is reduced.
Chapter 2. Architectural overview of SAP NetWeaver with DB2 for z/OS 21