True Delta Loads of R/3 Master and Transactional Data: How It’s Done When No Standard Extractors Are Available
- by Satish Chalasani, Independent BW/SEM Consultant
- September 1, 2003
You might typically extract R/3 master and transactional data for which no standard extractors exist based on timestamps or as a full load. Neither method captures all the data, however. A true delta load is possible using Application Link Enabling (ALE) message types. The author describes two undocumented options for building an ALE-based extractor.
SAP presents few options for performing delta loads to BW from R/3 master or transactional data for which no Business Content extractors exist. This could be data from R/3 standard tables or from one of the several Z-tables you have in your R/3 system. You might typically extract this type of data as a full load nightly or monthly, or you might do a delta load based on timestamps.
Neither method performs a true delta load, however. A full load captures all changes, but it is inefficient because it transfers a lot of data unnecessarily. A delta update using timestamps can only identify new records in a table and cannot be used if the existing (old) records change or if no timestamp is in the table, which is the case most of the time. To achieve a true delta load for the described circumstances, you should use Application Link Enabling (ALE) message types.
Several of SAP's standard Business Content extractors use ALE message types to delta-enable their extractors; most of these are master data extractors. As you might have discovered, SAP has not documented how to perform a delta load using ALE without a standard extractor. I've discovered the secret through a lot of trial and error. What I've learned follows, and it applies to both BW 2.x and BW 3.x.
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