R/3 Master Data Extraction Using Function Module

Question

Hi Experts,
   Could you please let me know why & How (Detail procedure) to extract R/3 master data using function module.
  My team manager asked me to extract master data from R/3 for 3 more attributes of info object '0material' which is already defined as data target.
I would like to know why they are extracting data using function module
Thanks

Answer 1

The steps for  creating extractor using Function Module. I
1. Create new Function group (if you have already not done so) in Se80
2. Copy Function module "RSAX_BIW_GET_DATA_SIMPLE" with suitable name.
3. Change the code that populate data.
Following table may give you the guideline for parameters.
Parameter Description
I_REQUNR (import) BW provides this request identifier. It is a system-generated identifier in the form REQU_XXXXXX. BW uses this same identifier in all function module calls that relate to a single load.
I_DSOURCE (import) The name of the generic extractor
I_MAXSIZE (import) The maximum number of records that BW expects to be in each data packet
I_INITFLAG (import) A Boolean flag that indicates if this is the initialization (first) call to the function module
I_READ_ONLY (import) A test flag not needed in most extraction scenarios
I_T_SELECT (table) This table holds any selections from the BW InfoPackage. The function module should examine these selections and only return data that matches the selections.
I_T_FIELD (table) This table holds the fields that BW requests
E_T_DATA (table) The function module fills this table with data records. These records then return to BW as data packets. This table has the same structure as the extract structure defined in the generic DataSource.
NO_MORE_DATA (exception) The function module raises this exception when no more data is available
ERROR_PASSED_TO_MESS_HANDLER (exception) The function module raises this exception if an error occurred during the extraction. It alerts BW to check for error logs.
Change following code to put the selection fields
Select ranges
RANGES: L_R_CARRID FOR SFLIGHT-CARRID,
L_R_CONNID FOR SFLIGHT-CONNID.
Change following to populate data
OPEN CURSOR WITH HOLD S_CURSOR FOR
SELECT (S_S_IF-T_FIELDS) FROM SFLIGHT
WHERE CARRID IN L_R_CARRID AND
CONNID IN L_R_CONNID.
ENDIF. "First data package ?
Fetch records into interface table.
named E_T_'Name of extract structure'.
FETCH NEXT CURSOR S_CURSOR
APPENDING CORRESPONDING FIELDS
OF TABLE E_T_DATA
PACKAGE SIZE S_S_IF-MAXSIZE.
below links
Re: functionmodule
Re: FM for G. extractor
***Assign points if it helps.**
Regards
CSM Reddy