Solution : https://service.sap.com/sap/support/notes/493387 (SAP Service marketplace login required)
Key words : 
transaction se11 -> extras -> enhancement category, latest sap web application server, sap web application server, normal oss error message, abap syntax check takes, unicode-programs  abap checks, predefined extension category, potentially affecting customers, generates warnings pointing, extending database tables
Related Notes : 
       
| 1319517 | Unicode Collection Note | 
| 1108861 | Add. info. on upgrading to SAP CRM 5.0 SR3 ABAP | 
| 1108700 | Add. info. on upgrading to SAP SCM 5.0 SR3 ABAP | 
| 1071404 | Add. info.: Upgrade to SAP CRM 2007 ABAP | 
| 1039395 | Add. info.: Upgrade to SAP CRM 5.2 ABAP | 
| 1010762 | Add. info. on upgrading to SAP SCM 5.1 ABAP | 
| 996484 | Syntax error in LIBIPFNOTIF | 
| 975861 | Add. Info.: Upgrade to SAP SRM Server 6.0 ABAP | 
| 961513 | Add. Info.: Upgrade to SAP SRM Server 5.5 SR2 ABAP | 
| 961512 | Add. info. on upgrading to SAP SCM 5.0 SR2 ABAP | 
| 961511 | Add. info.: Upgrade to SAP CRM 5.0 SR2 ABAP | 
| 947991 | Add. info.: Upgrade to SAP CRM 5.1 ABAP | 
| 925240 | Add. Info. on upgrading to SAP SCM 5.0 SR1 ABAP | 
| 913849 | Add. info.: Upgrade to SAP CRM 5.0 ABAP SR1 | 
| 826488 | Enhancements to upgrade on SAP CRM 5.0 ABAP | 
| 826093 | Add. info. on upgrading to SAP SCM 5.0 ABAP | 
| 763880 | Upgrade and customer-specific enhancement of PC2* structures | 
| 760897 | Enhancement Category for the Structure VTRK_D2. | 
| 737800 | Enhancements to upgrade on SAP CRM 4.0 SR1 | 
| 737696 | Add. info on upgrade to SAP R/3 Enterprise 4.70 Ext. 2 SR1 | 
| 696026 | RSUPGDEC: Table ... illegally extended: Error "..." | 
| 684406 | Additional information on upgrading to SAP SCM 4.1 | 
| 637683 | Add info about upgrade to SAP R/3 Enterprise Core 4.70 Ext 2 | 
| 628205 | User Includes:Behavior within non-Unicode SAP R/3 Enterprise | 
| 603852 | Additional information about upgrading to SAP SCM 4.0 | 
| 587896 | Add. info on upgrade to SAP R/3 Enterprise Core 4.70 SR1 | 
| 553110 | User Exits: Behavior within non-Unicode R/3 Enterprise | 
| 513536 | Add. information on upgrade to SAP R/3 Enterprise Core 4.70 | 
| 504250 | Enhancement of infotypes in Enterprise | 
| 494441 | Enhancing IDOC structures in Unicode-enabled programs |