Hi Venkat,
This it process I usually follow.
1) Do the fields have to generate delta records?
YES: Are the fields in the standard SD tables associated to the extractor For example 2LIS_11_VAITM the tables would be VBAK, VBAP, VBKD, VBUK, VBUP?
YES: Can you add them using LBWE?
YES: Add them via LBWE.
NO: Then the entry in table TMCEXCFS for that specific extract structure has a status of "F". You can overwrite it to "" and the use LBWE to add it to your communication structure. SAP does not advice this as fields could result in incorrect key figures. I've done it to fields for 2LIS_02_SCL with no data corruption so it depends on what field and extractor. Next option is to enhance the communication structure and implement enhancement MCS10001.
NO: Are the fields in the standard SD tables associated to the extractor?
YES: Append extract structure and update via EXIT_SAPSLRSAP_002.
NO: Create custom extractor and enrich data in BW or Append extract structure and update via EXIT_SAPSLRSAP_002.
Regards,
Dae Jin