Writeable Views are Desupported.
Andrew Bay, July 14, 2020 - 11:35 am UTC
I found what I wanted, sort of. "Writeable" Materialized views. But because they share their syntax with Updatable, it is impossible to know which one it went with. These are also desupported features.
It is looking like I will need to just create the table and maintain it with merge statements and the occasional truncate-insert refresh. When I tried making the writeable views, it tried desperately to make it updateable and threw an error for a couple of the tables. "SQL Error: ORA-12013: updatable materialized view must be simple enough and have a materialized view log on its master table to do fast refresh
12013. 00000 - "updatable materialized view must be simple enough and have a materialized view log on its master table to do fast refresh""
It would be nice if the create materialized view had "FOR WRITEABLE" as an option that allowed an MView to be updatable for any query with the caveat that it always does a complete refresh replacing your modified data.