You should only modify the standard if your requirements cannot be fulfilled by either Customizing or Personalization, or by the exits or Business Add-Ins provided in the system.
Before making modifications to the standard, refer to the section on theModification Assistant.
For information on modifying SAP tables, consult the portion of the ABAP Dictionary documentation called
TheSAP Software Change Registration (SSCR) Procedure is used for registering all modifications to SAP source code and SAP Dictionary objects.
You should also consult the sectionsGeneral Development Organization and Notes on Modifying the Standard before modifying the standard.