Reclustering 

Use

Reclustering allows you to change the clustering of InfoCubes and DataStore objects that already contain data. You may need to make a correction if, for example, there are only a few data records for each of the value combinations of the selected MDC dimension, as the table is using an unnecessarily large amount of memory space. In order to improve the performance of database queries, you may want to subsequently introduce multidimensional clustering for InfoCubes or DataStore objects.

Integration

This function is only available for the database platform DB2 UDB for UNIX, Windows and Linux. You can use partitioning to improve the performance of other databases. For more information, see Partitioning.

Features

Reclustering InfoCubes

Upon 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 copy operation is completed, 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 affected active aggregates of the InfoCubes; they are reactivated after the conversion.

Reclustering for 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 copy operation is completed, 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. When you double-click, the relevant logs appear. The following functions are available from the context menu of the request or editing step:

·        Delete: You delete the clustering request, it no longer appears on the monitor and you cannot restart. All of the tables remain in their current state, therefore, the InfoCube or the DataStore object could potentially be inconsistent.

·        Reset Request: You reset the clustering request. This deletes all of the locks on the InfoCube and all of its shadow tables.

·        Reset Step: You reset the canceled editing steps so that they return to their original state.

·        Restart: You restart the clustering request in the background.

Background Information About Data Copying

By default, the system copies a maximum of six processes in parallel. The main process separates dialog processes in the background. These dialog processes each copy small data packages and terminate with a COMMIT. If a timeout causes one of these dialog processes to terminate, you can restart the affected copy operations, after you have altered the timeout time, by choosing Restart Reclustering Request.

Activities

You can access reclustering by using Administration in the Data Warehousing Workbench, or by using Environment in the InfoCube or DataStore object maintenance.

You can schedule repartitioning in the background by using Initialize. You can monitor the clustering requests by choosing Monitor.