The union command requires that the design is identical. I think what you would like to accomplish can be done with the merge command. The merge command will merge what is identical in primary and secondary databases, and ignore items in the secondary database that's not in the primary database. There is also a union merge, which will create a merged database with all components of primary and secondary databases. This is only available in IUS8..2, and I recommend using IUS8.2-s015 if you are planning to do a union merge.
To do a union merge
merge test1 test2 -output merged
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