Improved data availability

More users demand access to Db2 data every hour, every day. Data sharing helps you meet your service objectives by improving data availability during both planned and unplanned outages.

Because 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. As the following figure illustrates, when an outage occurs and 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.

Begin figure description. When a subsystem comes down in a two–member data sharing group, new application requests are automatically directed to the functioning member. End figure description. — Figure 1. Data sharing improves data availability during outages. If one member or an entire central processor complex (CPC) is down, work can be routed to another member.

While increasing data availability has some performance cost, the overhead for interprocessor communication and caching changed data is minimal. Db2 provides efficient locking and caching mechanisms and uses coupling facility hardware. A coupling facility is a special logical partition that runs the coupling facility control program. It provides high-speed caching, list processing, and locking functions in a Parallel Sysplex®. The Db2 structures in the coupling facility benefit from high availability.