Solution : https://service.sap.com/sap/support/notes/841460 (SAP Service marketplace login required)
Key words : 
installing custom system copy exports, symptom installing database instances, terms saplicense iseries os/400, /400 db2/400 sapinst reason, prerequisites backlevel versions, apply sap note 837942, central instance installation, sap system, database installation, temporary license
Related Notes : 
       
| 837942 | iSeries: User-Switch fails with tools and multiconnect | 
| 760166 | INST: SAP R/3 Enterprise 4.70X2 SR1 on IBM eServer iSeries | 
| 708864 | iSeries: SAPinst kit for system copy of 620 Products |