Solution : https://service.sap.com/sap/support/notes/179580 (SAP Service marketplace login required)
Key words : 
upgrade strategyif parameter rdisp/bufrefmode = sendon, importing special textswhen importing special texts, french documentationthe documentation modules na, job sap language-import-job-3, profile parameterrdisp/bufrefmode = sendon, profile parameter zcsa/installed_languages, database system sap db, import transport request a9bk000330, table ddlog requires approx, handling language-dependent texts
Related Notes : 
       
| 339250 | Incomplete language supplementation | 
| 325186 | Language import:long runtime in SMLT and LANG_IMP3 | 
| 207670 | Language not completely installed | 
| 187917 | R/3 4.6B Installation/Upgrade Simp. Chinese UNIX | 
| 187916 | R/3 4.6B Installation/Upgrade Trad. Chinese UNIX | 
| 187910 | R/3 4.6B Installation/Upgrade Korean UNIX | 
| 187907 | R/3 4.6B Installation/Upgrade Japanese UNIX | 
| 187700 | HRDSYS: Translations of documentation into Japanese | 
| 179373 | Additional info for upgrade to Rel.4.6B | 
| 154351 | Known problems during lang. import of patch texts | 
| 18601 | Frequently asked questions on language transport |