Rolling Up Data to a SAP NetWeaver BW Accelerator Index
As with relational aggregates, the data consistency of the InfoCube and SAP NetWeaver BW Accelerator index is based on request handling in the BW system. When you load new data packages (requests) into the InfoCube, these are not immediately available for use in a BW accelerator index for reporting purposes. As with aggregates, the process that writes new data to the BW Accelerator index is rollup.
If you replace the relational aggregates in an InfoCube with a BW Accelerator index, you do not have to make further changes in the process chains or other settings. The process and the associated programs are identical.
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New data packages (requests) have been loaded into an InfoCube.
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BW Accelerator indexes for this InfoCube have been activated and filled with data.
As with relational aggregates, you have to exit data rollup after loading transaction data.
When you rollup data for an InfoCube, the system first loads the new data into any aggregates that exist in the InfoCube, and then determines the delta of the missing records for all the tables that have an index in the BW Accelerator index of the InfoCube and indexes it.
For more information about the different execution modes for this activity, in particular the recommended execution types Including Rollup of Data Packages As a Process in a Process Chain and Starting Rollup of Data Packages Manually (see Rolling Up Data in Aggregates).
If new SIDs are generated when transaction data is loaded, the system also writes new records to the indexes of the S, X and Y tables. This is carried out by the BWA master data delta daemon.
You can define how often this is done using global parameter MD_JOBFREQUENCY. To do this, choose 
BW Accelerator 
Index Settings Change Global Parameters 
on the SAP NetWeaver BW Accelerator Monitor screen (transaction RSDDBIAMON2). The Maintain BWA Index Parameters screen appears. The default value is 180 seconds. For more information, see Indexing Process Tab Page.
When the system has indexed all the indexes successfully, the data of the most recent request is released for reporting.
In InfoCube administration, where you can see whether a rollup is missing, running or successful, the system does not differentiate between whether the InfoCube has aggregates or a BW Accelerator index.
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The compression of data packages after rollup, as performed with aggregates to improve efficiency (see Efficiently Loading Data to Aggregates in section Setting Automatic Compression), does not apply to BW Accelerator indexes because the data on the BW Accelerator server already exists in a read-optimized format. It can be useful however to rebuild the BW Accelerator index if the InfoCube is compressed heavily after rollup (see System Response Upon Changes to Data: SAP NetWeaver BW Accelerator Index under Compress).
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You can use delta indexes to speed up the rollup process. For information about optimizing the performance of BW Accelerator indexes that are used particularly frequently (see Improving Efficiency Using BW Accelerator Delta Indexes).