Solution : https://service.sap.com/sap/support/notes/705887 (SAP Service marketplace login required)
Key words : 
terms dbs/db4/allow_cancel iseries db2/400 as400, setting                    dbs/db4/allow_cancel=0, change takes effect starting, sql cancel default changed, iseries db2/400, lib_dbsl patch levels, symptom db4, default changed, sql cancel, cancel support
Related Notes : 
       
| 494086 | iSeries: Cancelling long-running database operations |