BW Star Schema

In Chapter 1, we introduced the concept of a star schema. In Chapter 2, Screen 2.31 showed an InfoCube data model. Armed with this information, the question then becomes:

What does the InfoCube data model look like at the database level?

In this section, we will explore the relationships between database tables. They will give us a clear idea of what the star schema looks like in BW. Again, we use a step-by-step procedure.

Work Instructions

Step 1. Run transaction SE11, enter /BIC/FIC_DEMOBC as the fact table name, and then click graphics/display1.gif.

 

 

Note

From Screen 4.3, we know that /BIC/FIC_DEMOBC is the name of the fact table.

If we are interested in only the table contents, and not the table definition, we can run transaction SE16 instead.
 

SCREEN 7.1

graphics/07fig01.gif

Step 2. The Check table column lists parent tables of the fact table. Double-click /BIC/DIC_DEMOBC3 to display the sales representative dimension table.

 

 

Note

BW uses D to name dimension tables.

  • DP is for the data packet dimension. We will discuss its role in BW in Chapter 12.
  • DT is for the time dimension.
  • DU is for the unit dimension.

SCREEN 7.2

graphics/07fig02.gif

Step 3. The dimension table does not have any check tables, but it has a field called SID_IO_SREP. Click graphics/displaytable.gif to display the table's contents.

 

 

SCREEN 7.3

graphics/07fig03.gif

Step 4. Click graphics/clock.gif to execute.

 

 

SCREEN 7.4

graphics/07fig04.gif

Step 5. Notice that SID_IO_SREP 11 corresponds to DIMID 23.

From Screen 4.4, we know that DIMID 23 is the value of the field KEY_IC_DEMOBC3 in the first row of the table /BIC/FIC_DEMOBC.

Then what does SID_IO_SREP 11 represent?

 

 

SCREEN 7.5

graphics/07fig05.gif

Step 6. Repeat Step 1 to display the contents of IO_SREP's SID table, /BIC/SIO_SREP. This screen shows the SID table definition. Click graphics/displaytable.gif to display the table's contents.

 

 

SCREEN 7.6

graphics/07fig06.gif

Note

Here SID is Surrogate-ID, not the System ID used to name an SAP system.BW uses S to name a characteristic's SID table.

Step 7. The contents of the SID table /BIC/SIO_SREP are displayed.

In this screen, we see that SID 11 corresponds to SREP01, a sales representative ID in the first record of Table 3.3.

 

 

SCREEN 7.7

graphics/07fig07.gif

Following the same approach, we can discover the relationships between the SID table /BIC/SIO_SREP, the master data table /BIC/PIO_SREP, and the text table /BIC/TIO_SREP. The contents of the latter two tables are shown in Screens 7.8 and 7.9.

Step 8. Repeat Step 1 to display the contents of IO_SREP's master data table, /BIC/PIO_SREP. This screen shows the table's contents.
 

SCREEN 7.8

graphics/07fig08.gif

Step 9. Repeat Step 1 to display the contents of IO_SREP's text table, /BIC/TIO_SREP. Screen 7.9 shows the table's contents.

 

 

SCREEN 7.9

graphics/07fig09.gif

Step 10. Repeat Step 1 to display the contents of IO_SREP's hierarchy table, /BIC/HIO_SREP. Screen 7.10 shows the table's contents.
 

Note

Screen 7.10 shows the contents of the hierarchy table, /BIC/HIO_SREP. Unlike the master data table and the text table, the hierarchy table does not link to the SID table. BW builds the hierarchy based on the information in the tables /BIC/IIO_SREP, /BIC/KIO_SREP, and /BIC/SIO_SREP.

SCREEN 7.10

graphics/07fig10.gif

Result

Based on our discussion, we can draw a simplified star schema as shown in Figure 7.1.

Figure 7.1. BW STAR SCHEMA FOR PART I INFOCUBE DESIGN

graphics/07fig01a.gif

In Figure 7.1, the solid lines are the true masterdetail relationships, reinforced by foreign keys. The dashed lines are relationships that are maintained by ABAP programs, but not reinforced by foreign keys.

The dashed-line relationships allow us to load transaction data even when the database does not contain any master data. Screen 7.11 shows the InfoPackage used in Section 3.9. Under the Update parameters tab, notice the Always update data, even if no master data exists for the data option.

SCREEN 7.11

graphics/07fig11.gif

With this star schema in mind, let's look at three InfoCube design alternatives.

Part I. Guided Tours

Business Scenario and SAP BW

Creating an InfoCube

Loading Data into the InfoCube

Checking Data Quality

Creating Queries and Workbooks

Managing User Authorization

Part II. Advanced Topics

InfoCube Design

Aggregates and Multi-Cubes

Operational Data Store (ODS)

Business Content

Generic R/3 Data Extraction

Data Maintenance

Performance Tuning

Object Transport

Appendix A. BW Implementation Methodology

Object Transport

Appendix B. SAP Basis Overview

Object Transport

Appendix C. Glossary

Appendix D. Bibliography



SAP Bw. A Step-By-Step Guide
Sap Bw: a Step By Step Guide for Bw 2.0
ISBN: B000LZM8CM
EAN: N/A
Year: 2002
Pages: 106

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