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Function documentationImproving Efficiency Using BWA Delta Indexes Locate this document in the navigation structure

 

You can create a delta index for each SAP NetWeaver BW Accelerator index. If a delta index exists, the system does not write to the main index during each delta indexing or each indexing activity (except the initial filling/indexing) and the main index is not optimized. Instead, the system writes data to a second index which has the same structure as the main index but is usually smaller. The smaller the delta index, the faster the subsequent optimize procedure and therefore the whole process of rolling up data or making modifications after a hierarchy or attribute change run.

Recommendation Recommendation

As read performance deteriorates the larger the delta index gets, we recommend only activating the delta index for essential indexes like fact indexes and X/Y indexes. This improves performance when you modify data after a hierarchy or attribute change run.

End of the recommendation.

Integration

We recommend that you regularly merge the delta indexes with your main index so that read performance is not negatively affected. You can do this in several ways:

  • On the Analysis and Repair of BW Objects screen (transaction RSRV), test area   BW Accelerator   BW Accelerator Performance  , you can select the Size of Delta Index elementary test. Choose Correct Error to access repair mode and then execute a MERGE for the indexes. For more information about analyzing BW accelerator indexes in the analysis and repair environment, see Tests for BWA Indexes in Transaction RSRV.

  • You can schedule the program RSDDTREX_DELTAINDEX_MERGE.

Activities

To set the delta index for a BW accelerator index, call the BW Accelerator Monitor screen (see Monitoring BWA Indexes) and choose   BW Accelerator   Index Information   Set Delta Index  . The Delta Index Properties dialog box appears.

Switching On the Delta Index

In the Delta Index column, set the relevant flag if you want the table to use a delta index.

The new setting takes effect with the next delta indexing operation.

Switching Off the Delta Index

You reset the setting for the delta index in the same way.

Before the next indexing operation, the system merges the delta index and the main index. If the delta index is already very large, the next process may take longer.