Tuning of BWA FEMS compression
Within this blog (maybe
there will be more posts) I want to focus on performance issues with SAP Business Warehouse Accelerator (BWA) .
Some experienced BWA admin
may just laugh seeing this post. However there are some customers out there not
knowing about this feature of BWA. The fact is that FEMS compression is BWA
feature aimed for reduction of transport costs. This is meant in terms of an
intelligent compression schema. Moreover elimination of duplicates in query
results directly on the BWA side is enabled. Setting this feature ON can
improve performance of BWA.
FEMS are Formula EleMent Selections (or also Finite EleMent Solver) carrying information about structure
elements where certain value belongs. Database and BWA are giving records by
exploding structure elements. These records are than assigned to correct
structure elements by the OLAP. FEMS compression enables merge of duplicate
structure elements in BWA part and makes OLAP par being able to process this information.
All together there is a reduction of information traffic between BWA and BW
backend.+). Open screen area Landscape -> Ini. See current
to set this setting? </p><p>See above *configuration file +TREXIndexServer.ini.
Add parameter in to file: fems_compression = on.+
In general settings FEMS
compression ON is always advisable. Setting this ON has no influence on BWA’s indices
size. You may only be asked by SAP to switch it off in situation that you
raised BWA problem message (e.g. wrong data provided by BWA based query vs. proper
data given by same query running without BWA) to SAP via SMP channel. If issue cannot be quickly
analyzed SAP may ask you to switch compression off to help them isolate issue.
sources used for this blog:*