2942068 - Significant performance degradation of insert .. select statement after upgrading from IQ 15.4 -- SAP IQ

There is a significant performance degradation of insert .. select statement after upgrading from IQ 15.4.

SQL has following typical structure.
   insert into "owner"."table"( .. ) select .. from "owner"."table_wrk" where predicate1 = .. and predicate2 = ..;

Target table "owner"."table" is huge with row count of 5,984,731,600 and 12 HG indexes.
All indexes are rebuilt after upgrade.

Various performance tuning choices did not help.
- Lowering SORT_PINNABLE_CACHE_PERCENT.
- Toggling HGs from HG to THG.
- varchar width optimization option DML_options14=8. There are couple of large varchar columns with HG indexes.
- CORE_Options156 = ON which is a workaround for similar CR 818641

IQ 16.0 sp11 pl20+

insert select , performance , WaitForSignal_DontCareIfBusy , dfo_THGMerge , KBA , BC-SYB-IQ , Sybase IQ , Bug Filed