Solution : https://service.sap.com/sap/support/notes/1157472 (SAP Service marketplace login required)
Key words : 
tools --> specification management --> specification database structure --> settings, health & safety -> dangerous goods management -> basic data, img activity 'activate sap ecc extensions', system issues error message dg 129, dangerous goods user-defined textssolution, health & safety --> basic data, create dangerous goods master records, check/modify dangerous goods data, change dangerous goods master data, activate sap ecc extensions
Related Notes : 
       
| 1223650 | Message CB01 203 and the check to see if EH&S is active | 
| 1048850 | Missing values after you import a dangerous goods master | 
| 1010878 | Conversion report for value indic. in dangerous goods master | 
| 964556 | Missing quantities when you import UN-listed substances | 
| 858271 | Upgrading to EH&S in ERP 2005/ERP 6.0 | 
| 855959 | Activation of Extension Sets via SPRO not successful | 
| 816806 | SAP ECC 5.0 Enterprise Extensions: Activation switch | 
| 746211 | Upgrade to EH&S in ERP 2004 | 
| 692664 | Dangerous goods: Upgrade EH&S 2.2B to higher EH&S versions | 
| 666925 | SAP R/3 Enterprise Extension Set 200: Activation switch | 
| 642614 | EH&S: Upgrade to SAP R/3 Enterprise PLM 2.00 | 
| 564926 | EH&S: Upgrade to SAP R/3 Enterprise PLM 1.10 | 
| 535003 | SAP R/3 Enterprise Extension Set 1.10: Activation switch | 
| 527925 | Use of collective mode-of-transport categories |