Some tables that are heavily updated on the source during a full reload of that table on the target, generate duplicate insert errors.
This is a known issue described in much detail in the QLIK KB here.
However, since version 6.6 the workaround described in that article no longer works, and produces an error. The syntax of the string that needs to be put in the table settings has changed.
I open this request to have this formally implemented as a feature/option that should be enabled by default for DB2 z/OS or DB2 AS/400 databases. Currently it is a "hidden" internal feature to workaround this issue, and thus not supported and not stable.
It is crucial for our business that this gets implemented.
Related case: 02138955 - INITIAL LOAD FAILS WITH DUPLICATE INSERT ERRORS WHILE APPLYING CACHED EVENTS.