Solution : https://service.sap.com/sap/support/notes/68440 (SAP Service marketplace login required)
Key words : 
operating system releases prior, current sap release strategy, older sap database release, operating system release ibm, released operating systems, operating system release, 1 customer systems based, product availability matrix, sap support portal, 3-tier sap systemshere
Related Notes : 
       
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| 376510 | iSeries: V5R1: SQL0030 error in SDB1FDB4 | 
| 202169 | Additional Info: Upgrade to 4.6C - DB2/400 | 
| 178823 | Additional Information: Upgrade to 4.6B - DB2/400 | 
| 162117 | Additional Information: Upgrade to 4.6A - DB2/400 | 
| 141661 | Additional Info: Upgrading to 4.5B DB2/400 | 
| 108377 | Additional Info: Upgrading to 4.5A DB2/400 | 
| 99379 | Additional Info: Upgrading to 4.0B DB2/400 | 
| 86062 | Additional Info: Upgrading to 4.0A DB2/400 |