Multiple Db2 instances, or “members” accept and service incoming Db2 work with all of them accessing a single copy of the data.
To stop multiple processes all updating the same data the PowerHa pureScale Server (also known as the Coupling Facility) is responsible for co-ordinating the activities of all of the Db2 members in the pureScale group.
The CF holds shared locking information and cached data pages of interest to one or more members of the group. Each member has direct access to the CF via an InfiniBand high-speed network interconnect, minimizing the performance overhead.
Db2 pureScale has been designed to minimise the impact to the applications running in the cluster. No complex re-writes are required and so extra capacity easily be added with no interruption to service.
With Db2 pureScale technology, you can grow and shrink your cluster on demand, as your business needs grow or subside. Along with flexibility, Db2 pureScale offers breakthrough efficiency. To demonstrate this, IBM scaled Db2 pureScale technology out to 128 members on IBM Power systems.
Results show near linear scaling out to 128 members in the cluster:
This allows work to be intelligently distributed to various member Db2 systems based on how busy each one is.
It is possible to run to coupling facilities in a duplexed arrangement, with Db2 automatically keeping primary and secondary CF in syc. With dual CFs and multiple Db2 members all hosted in separate physical boxes a CF or a physical disk still allows processing to continue this providing true “active/active” Db2 clustering.
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