Enhancing DataSource

General Steps to Enhance DS:
1. Enhance Extract Structure (Append Structure)
2. Implement Customer exit 
    a) CMOD create enhancemnet project
    b) Assign enhancemnet to project
    c) Implement exit
3. Re-generate DS. (RSA6 -> Change the DS -> DataSource -> Generate)
4. Customizing for extraction (Replicate Datasources from a source system will create identical DS structures in the BW system.)
4. Checking Extractors & Loading data

Reference:
1. Enhancing LO Datasource Step by Step with screen shot and code:
https://www.sdn.sap.com/irj/sdn/go/portal/prtroot/docs/library/uuid/b0af763b-066e-2910-a784-dc6731660f46

2. SAP help documnet about enhancing DS
http://help.sap.com/saphelp_nw70/helpdata/en/6e/fe6e420f00d242e10000000a1550b0/frameset.htm 

3. Business Content
http://help.sap.com/saphelp_nw70/helpdata/en/c1/ea683cc5e8ca68e10000000a114084/frameset.htm

Code Example (Customer exit):
DATA: l_s_mat LIKE biw_mara_s, "Provider Structure for Material Master Data
          l_tabix LIKE sy-tabix,
          l_prctr LIKE marc-prctr.

CASE i_datasource.

WHEN '0MATERIAL_ATTR'.

    LOOP AT i_t_data INTO l_s_mat.

      l_tabix = sy-tabix.

      SELECT SINGLE prctr
        INTO l_prctr
        FROM marc
        WHERE matnr = l_s_mat-matnr.

      IF sy-subrc = 0.
        l_s_mat-prctr = l_prctr.
      ELSE.
        l_s_mat-prctr = ''.
      ENDIF.

      MODIFY i_t_data FROM l_s_mat INDEX l_tabix.
    ENDLOOP.
ENDCASE.

Other：
1. RSA5/RSA6的区别。
从BI中选Customizing Extrators会Navigate到Source System中的RSA6. RSA6中的DS都是A version。
RSA5中保含未激活状态的DS, 可在此transaction中activate DS.

NOTE: DS in R/3 source system come in two versions
    a) D - SAP delivery version
    b) A - Active version
The D version is the original definition from the Plug-In. The A version is used in data extraction.

The R/3 Plug-In (PI) must be installed in the source system. The Plug-In interface enables the exchange of data between SAP systems. Technically, the Plug-In contains ABAP Objects, such as tables and programs, used for data extraction.

Tips: If you want to find a specific DS, you shoud
    a) Position the cursor on the root node
    b) Click "Expand" button on the application toolbar
    c) Click "Find" in the system app toolbar
This way we can find DS quickly.

2. Delta update的处理细节
3. 如何在R/3 source system中创建一个新的DS
    a) SBIW -> Generic DS -> Maintain Generic DS  or RSO2 to create DS
    b) Replicate the DS so that identical structures of the DS can appear in the BW system