Solution : https://service.sap.com/sap/support/notes/71092 (SAP Service marketplace login required)
Key words : 
menu path sales --> sales documents --> define variable messages, salesauthorization groupdevelopment class     $tmp temporary objects, applicationselection screen version  upper/lower case, fixed point arithmetic  editor lock              start, customer function exit_saplved4_001 - customer enhancement ved40001, additional key words component supplier processing, delivery schedules/jit delivery schedules, define customer-specifically, jit delivery schedules, delivery schedule processing
Related Notes : 
       
| 523457 | |
| 88713 | Some variable messages cannot be customized | 
| 74055 | Variable messages: Version maintenance |