Making changes to the Teradata QueryGrid configuration can potentially impact production workloads, so Teradata QueryGrid supports the ability to test configuration changes before those changes are activated. After the configuration change is tested and verified, it can be activated so that it becomes available to production workloads.
Changes to configuration entities (fabrics, connectors, links, communication policies, and networks) are versioned. When a query starts, it resolves which versions of the configuration entities it will use. These versions are passed around to all components executing on behalf of that query, so that all components use the same version of the configuration.
When a configuration change is made, it may take some time for that change to reach all the components of a system. If a query references a version of a configuration entity that has not been propagated throughout the system, the query will fail. Configuration changes should be persisted and tested before being applied to production workloads, to make sure the configuration change is distributed to all the components of Teradata QueryGrid.
Configurations can be in one of three states: active, pending, and previous. Active is the tested and verified actively running version of the configuration. Pending is used for testing new or modified configurations. Active configurations are put in a previous state when another version of the configuration is activated.
If you replace an active version, the formerly active version becomes the previous version and the former previous version is deleted. If you activate a pending version, the formerly active version that you replaced becomes the previous version. If you activate a previous version, the active version becomes the previous version, and any pending version remains the pending version.