转：SAP就是BI的黑洞

除非你买了BW和“足够”的咨询，否则就是一个噩梦。。。这是第一线的人员告诉我的


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Special Considerations for SAP
Because of the marketplace dominance of SAP as an ERP system, we get asked
about the role of SAP in the data warehouse. Here are our unvarnished
recommendations.
You have probably heard the clich ´e that, from a decision-support standpoint, SAP
ERP is like a black hole: Rivers of data flow in, but there is no way to get the
information back out. Why?
A contemporary SAP ERP implementation is likely to have a data foundation that
consists of tens of thousands of physical tables, exhibiting few DBMS-defined
table relationships, with entity and attribute names rendered in abbreviated
German! Thus, the SAP RDBMS, for all practical purposes, is incomprehensible and
proprietary. SAP ERP comes with an extensive library of operational reports, but
these typically fall short of fully addressing the decision-support needs of most
business communities. This is not a design flaw. SAP’s OLTP data architecture
simply lacks support for fundamental business-reporting needs, such as historical
retention of transactions and master data images, comprehensible and easily
navigated data structures, and robust query performance characteristics.

Some early SAP adopters tried to free their operational data trapped inside the
ERP labyrinth by creating ERP subject areas in their data warehouses, populated
via hand-crafted ETL. Predictably, with few specialized tools to assist them in this
heroic undertaking, many of these efforts achieved unremarkable degrees of
success.
Recognizing this unmet and blossoming need, SAP created a decision-support
extension to their ERP application called the Business Information Warehouse
(SAP BW). Early generations of SAP BW were rather primitive and consisted mainly
of SAP-specialized ETL feeding proprietary OLAP repositories, thus lacking many of
the foundational architectural elements of the contemporary data warehouse.
Newer releases of SAP BW have evolved considerably and now embrace many of
the core tenets and structures of contemporary data warehousing: better support
for non-SAP data sources and persistent mainstream data repositories (Staging
Areas, ODS, Data Warehouse, Dimensional Data Marts, and OLAP cubes). Some of
these repositories support open access by third-party reporting tools.
SAP BW value proposition, at face value, now offers a compelling price and
timeframe sales story that is likely to attract the attention of CIOs. And so, the
contemporary DW architect will likely be asked to define and defend a role for SAP
BW within the corporation’s overall data warehousing vision.
In the following table, we present pros, cons, and recommendations for several
SAP BW role scenarios within an overall enterprise DW strategy. We humbly
recognize that this is a rapidly evolving area, with many variables, in which fewfully satisfactory solutions exist. BW and ETL tool capabilities will change, thereby
modifying the decision balances that follow. But we hope nonetheless that our
evaluation process will be useful to you and extensible to your unique situation
and challenges.