While
loading data into SAP BW systems one aspect of it comes to the picture. It is
the one related to sequence of data loading. Normally in general the data
loading sequence shall be like following. Master data loads come first followed
by transactional data loads.
Loading
sequence within the master data (MD) shall be as follows. First to load MD attributes
then texts and finally hierarchies. But the attributes and texts can be loaded
in parallel. Due to more complex operation while loading of the hierarchies are
going on I suggest to put the hierarchy loads as last step of MD loads.
Now
on topic of loading MD before transaction data (TD). All MD shall be loaded
before TD is loaded. If it is not the case the TD loads triggers insertion of MD
rather empty master data entry. What is meant by insertion here is that SID
needs to be generated for the characteristic attributes, and new records have
to be inserted in the MD tables.
This can cause performance issues as the load
can take twice as much due to inserting the MD during load of TD. Also if there
are parallel loads in place there may locks appear in SID table update. Another
issue that can happen is while there are master data lookup in the transformation
of the TD. If the MD is not present then there is nothing to be looked up and as
a result there is a data quality issue.
More
information:
652856 - Loading
hierarchies with process chains
1597364 - FAQ:
BW-BCT: Extraction performance in source system
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