Solution : https://service.sap.com/sap/support/notes/215296 (SAP Service marketplace login required)
Key words : 
nt-intel windows nt enterprise edition ii/ actions prior, nt-intel windows nt enterprise edition, platform            release 32 bit        64bit          ================================================          aix                  7, additional key words upgrade informix, upgrade 0/ informix dynamic server version, database softwareii/ actions prior, individual upgrade phasesv/ actions, ===============0/ informix dynamic server version, uc4ax1    -          windows nt, individual operating system platforms
Related Notes : 
       
| 338276 | Additional information: Upgrade to BW 2.1C | 
| 213865 | Additions to upgrade to BW 2.0B |