The information provided applies to the Informix Server Version 11.70.xC4 and later.
To refresh the data in a data mart of the Informix Warehouse Accelerator, the data mart must be loaded with a new set of the complete data. This can be done by dropping the existing data mart, re-creating it and then loading it with the new data. Alternatively, the data mart can be disabled and loaded. While this saves the procedure of dropping and re-creating the data mart, it still means that the data mart is not available during the loading of the new data. And as normally this loading phase is the step that takes the longest, renewing the data always renders the data mart unavailable for considerable time.
Fortunately, with version 11.70.FC4 of the Informix Server, it is now possible to achieve continuous availability of a data mart even during the procedure of renewing the data. For this, a second data mart with the same definition, but a different name, needs to be created and loaded. While this new data mart is being loaded, the old data mart is still available for query acceleration. As soon as loading of the new data mart is complete, the new data mart will become active. From that moment onwards it will be utilized for the acceleration of newly arriving queries. This switch over to the new data mart happens automatically in the optimizer of the Informix Server, where it is decided, whether a query can be accelerated. As soon as the last query utilizing the old data mart has completed, the old data mart can be dropped manually.
With this method, queries can be continuously accelerated even while new data is being loaded. It should be noted however, that this method of data refresh requires the double of the memory space needed normally for the data mart, though only for a short time. Therefore the size of the shared memory available for the worker nodes may need to be adjusted accordingly. Parameter WORKER_SHM in the accelerator's configuration file "dwainst.conf" specifies the relevant memory resource.
Also see the description in the manual "IBM Informix Warehouse Accelerator Administration Guide".