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A complete WebSphere high availability solution also requires other components that WebSphere interacts with, to be highly available. These components can be DB2, WebSphere MQ, and so on.
The high availability solution for DB2 on z/OS is DB2 Data Sharing. See Figure 8-8. This function enables multiple applications to read from, and write to, the same DB2 data concurrently. The applications can run on different DB2 subsystems residing on multiple Central Processor Complexes (CPCs) in a Parallel Sysplex.
Figure 8-8 A DB2 Data Sharing Group in a sysplex
DB2 data sharing improves the availability of DB2 data, extends the processing capacity of your system, provides more flexible ways to configure your environment, and increases transaction rates. You do not need to change the SQL in your applications to use data sharing, although you might need to do some tuning for optimal performance.
Data sharing provides multiple paths to data, a member can be down, and applications can still access the data through other members of the data sharing group. When one member is down, Transaction Managers are informed that the member is unavailable, and they can direct new application requests to another member of the group. For more information about DB2 for z/OS Data Sharing, see the DB2 InfoCenter at:
http://publib.boulder.ibm.com/infocenter/dzichelp/index.jsp
