-7066: Unique index referenced by foreign key not allowed
Explanation:
The specified index cannot be deleted, because the columns contained in it were specified as referenced columns of the REFERENCED TABLE in a REFERENTIAL CONSTRAINT DEFINITION.
User Action:
The index can only be deleted after deleting the corresponding REFERENTIAL CONSTRAINT DEFINITION. Use a <QUERY statement> issued on the system table DOMAIN.COL_REFS_COL to find out which <CONSTRAINT definition>s are defined.