DB2 data sharing lets an application run on one or more DB2 subsystems in a Parallel Sysplex environment. The applications can read and write to the same data at the same time.
Data sharing is new concept, earlier we used Distributed Data Facility (DDF) to access data on other subsystems, or we employed other, more creative means, such as replication between subsystems.
The subsystems that can share data must belong to a data-sharing group. The subsystems in the group are known as members. A data-sharing group can have up to 32 members. Only members in the group can share data, and each member can belong to only one group.
DB2 data sharing operates in a Parallel Sysplex environment, which is a cluster of z/OS systems that can communicate with each other.
Some important components enable this communication to occur and ensure the consistency and coherency of the data being shared between the subsystems in the group.
All members share the same DB2 catalog and directory and the same user data, which must reside on shared DASD.
Shared Data Architecture (SDA) is the architecture behind DB2 data sharing. SDA is based on coupling technology that enables the use of high-speed coupling facility channels, reduced system-to-system communications (message passing), multiple paths to the data for higher availability, and dynamic workload routing based on capacity rather than location. SDA doesn’t require data partitioning for growth, and it doesn’t rely on node-to-node communications for resources.