Changing standard SAP tables

Question

can any one tell me what is the difference between Append Structure and Custom Includes for the purpose of modification in standard SAP tables

Answer 1

Append structure :
+Append Structures Locate the document in its SAP Library structure
Append structures are used for enhancements that are not included in the standard. This includes special developments, country versions and adding customer fields to any tables or structures.
An append structure is a structure that is assigned to exactly one table or structure. There can be more than one append structure for a table or structure.
The following enhancements can be made to a table or structure TAB with an append structure:
· Insert new fields in TAB,
· Define foreign keys for fields of TAB that already exist,
· Attach search helps to fields of TAB that already exist,
These enhancements are part of the append structure, i.e. they must always be changed and transported with the append structure.
When a table or structure is activated, all the append structures of the table are searched and the fields of these append structures are added to the table or structure. Foreign keys and search help attachments added using the append structure are also added to the table. If an append structure is created or changed, the table or structure assigned to it is also adjusted to these changes when the append structure is activated.
Since the order of the fields in the ABAP Dictionary can differ from the order of the fields on the database, adding append structures or inserting fields in such append structures does not result in a table conversion.
The customer creates append structures in the customer namespace. The append structure is thus protected against overwriting during an upgrade. The fields in the append structure should also reside in the customer namespace, that is the field names should begin with ZZ or YY. This prevents name conflicts with fields inserted in the table by SAP.
If you create an append structure for a table or structure, only those enhancements are allowed that are consistent with the enhancement category of the enhanced table or structure. For more information, see Structure linkStructure Enhancements.
The new versions of the standard tables are imported after an upgrade, and the fields, foreign key definitions and search help attachments contained in the append structures are added to the new standard tables at activation.+
Custom include
These are includes in SMOD Enhancements, any of these appear on database transparent table but also in structure used by FM, BAPI. They are activated in a project and SAP usually provide user-exit or BADI to maintain/Exploit the added fields in the same enhancement..
e.g: CI_EKPODB in SMOD MM06E005
Look also at HOWTO:Implement a screen exit to a standard SAP transaction
Regards