DTP Performance Improvement: Semantic Groups

 Semantic groups can be set in DTP in the extraction tab. These are the fields from the source which are available for selection as semantic keys.

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The BW system while doing the loads will group the data based on these semantic keys for a data packet and then will perform the load process package by package.

The setting up of semantic keys can enhance or reduce the DTP performance, hence these should be used carefully.

In a scenario where there is a start routine which is sorting the source package and looking up a table based on certain key fields, it is good idea to use the semantic groups.

I have seen that the loads which were taking more than 5 hours with parallel extraction from source to target DSO, took less than 30 minutes with semantic groups and lesser package size.

Usually the long start routines are causing the issue for increase in load times, it is always good to use semantic groups and smaller package size in such cases.

If there are no start or end routines and large number of fields are there in the data being loaded to cube with minimal field routines, semantic groups will not help to improve the performance. Instead, these can increase the load times.

Hence care should be taken when activating semantic groups in a DTP.

Note: If error handling is activated in a DTP, semantic groups are automatically generated by the bw system. These work as primary keys for the error stack.Therefore, error handling should be activated only when required, or else the load performance can suffer.

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