Database-Centric Data Warehouse:
In the database centric approach we have to make a copy of an R/3 database for users to report against. Conceptually, the idea is simple, but it is an operations keeping R/3 OLTP and R/3 reporting in synch is very difficult.
The benefit of this model is that you will have no performance degradation on your R/3 OLTP environment due to reporting and data analysis activities. We can define special user authorization and profiles for reporting users . This R/3 can also become the data source for intra-application data instead of OLTP R/3.
The problem in this approach is that we you have access to only the data that exists in the OLTP instance that is we have no historical data to report on. Moreover, we will face the same limitations and complexities of R/3 information systems and reporting tools that are not Web enabled. This database-centric approach will be an expensive proposition due to additional hardware and intense operations tasks to keep both instances operational at all times.
ALE-Centric Data Warehouse
In this model we do not copy a full database but rather use ALE to propagate specific changes into the reporting environment-another R/3 instance.
Based on the customer's business model, ALE packages transaction and/or master data in the form of Intermediate Documents (IDOCs). IDOCs are data containers similar to EDI standard documents. The figure below shows an example of how a MNC used this approach to implement an ALE-based reporting environment .
Here four individual R/3 instances were connected via ALE:
- R/3 instance to manage master data.
- R/3 instance for financial operations.
- Instance for logistics operations.
- Instance for reporting.
Under this model, special SIS structures and special ledger structures are transferred to reporting instances using ALE, copy management, and some homegrown techniques to synchronize objects across all instances. ALE copied new changes in the reporting instance at 10-minute intervals.
Additional SIS structures were updated within the reporting instance using copy management techniques to build additional tables containing several levels of aggregated data for reporting. This enabled end users to access near real-time data without impacting performance on the R/3 OLTP operations. For corporate central data warehouses, new data was extracted from the reporting instance instead of the R/3 OLTP instance.
The ALE centric reporting environment advantages:
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Contains only that data required for reporting and analysis. It is not an identical copy of OLTP R/3 instances.
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Can accumulate historical data.
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Can import non-R/3 data for reporting.
The disadvantages of this environment are :
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Has the same inflexible R/3 reporting tools.
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Requires additional application servers to manage ALE traffic for all four instances.
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ALE technology is not rich and mature enough to handle large data volumes and user-specific data objects.
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Physical database implementation is still R/3-transaction-centric. Has no true multidimensional star data structures.
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Is heavy on hardware/software/network resources.
Third-Party-Tool-Centric Data Warehouse:
Third-party data extraction tools work to a point when transaction and associated data volume is small and business rules/configuration behind such data sets is simple. Some data extraction tools extract data at the database level, leaving critical data behind in pool and cluster tables
Often, the ABAP code generated by these tools is not optimized enough to fetch and transport data in the most efficient manner. One of the major problems in implementing a third-party solution is that the OLTP and data warehouse/OLAP teams do not share the same infrastructure.
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