Hi Symala,
1) Use this -> http://scn.sap.com/docs/DOC-69675 . (https://youtu.be/m5qJWKQprJM)
2) The above doc can be referred, where an “execute” method can be ABAP modified to restrict the file size .
3) Ask Abaper to check for “SAVE” method too if it exists.
Please keep posting to response.
Thanks,
Kolusu