Reclustering
Reclustering allows you to change the clustering of InfoCubes and DataStore objects that already contain data. You might need to make a correction, for example if there are only a few data records for each of the value combinations of the selected MDC dimension, causing the table to use an excessive amount of memory space. To improve the performance of database queries, you might want to introduce multidimensional clustering for InfoCubes or DataStore objects.
This function is only available with database platform IBM DB2 for Linux, UNIX, and Windows. You can use partitioning to improve the performance of other databases. More information: Partitioning.
Reclustering InfoCubes
With reclustering, the InfoCube fact tables are always completely converted. The system creates shadow tables with a new clustering schema and copies all of the data from the original tables into the shadow tables. As soon as the data is copied, the system creates indexes and the original table replaces the shadow table. After the reclustering request has been successfully completed, both fact tables exist in their original state (name of shadow table) as well as in their modified state with the new clustering schema (name of original table).
You can only use reclustering for InfoCubes. Reclustering deactivates the active aggregates of the InfoCubes, which are then reactivated again after conversion.
Reclustering DataStore Objects
Reclustering completely converts the active table of the DataStore object. The system creates a shadow table with a new clustering schema and copies all of the data from the original table into the shadow table. As soon as the data is copied, the system creates indexes and the original table replaces the shadow table. After the reclustering request has been successfully completed, both active tables exist in their original state (name of shadow table) as well as in their modified state with the new clustering schema (name of original table).
You can only use reclustering for standard DataStore objects and DataStore objects for direct update. You cannot use reclustering for write-optimized DataStore objects. User-defined multidimensional clustering is not available for write-optimized DataStore objects.
Monitor
You can monitor the clustering request using a monitor. The monitor shows you the current status of the processing steps. By double-clicking, you can view their logs. The following functions are available in the context menu of the request or editing step:
Delete: The clustering report is deleted. It no longer appears in the monitor, and it is not possible to perform a restart. All tables remain in their current state. This might cause inconsistencies in the InfoCube or DataStore object.
Reset Request: The clustering request is reset. This deletes all the locks for the InfoCube and all its shadow tables.
Reset Step: Canceled editing steps are reset to their original state.
Restart: The clustering request is restarted in the background.
Background Information About Copying Data
In the default setting, the system copies a maximum of six processes in parallel. The main process splits dialog processes in the background. These dialog processes each copy small data packages and finish with a COMMIT. If a timeout causes one of these dialog processes to terminate, you can restart the relevant copy operations after modfying the timeout time. To do this, choose Restart Reclustering Request.
You can access reclustering in the Data Warehousing Workbench under Administration or in your InfoCube or DataStore object's context menu.
You can schedule reclustering in the background by choosing Initialize. You can monitor the clustering requests by choosing Monitor.