After upgrading the Oracle database from 10g to 19c, I'm experienced the performance issue with Toad as querying in dual (temporary table) and views on a large database (update/ insert statement). I've to wait for more than a hour when comparing the performance of views in Oracle database 10g.
Any help would be appreciated.
I don't mean to brush you off, but this sounds more like a case for Oracle support than Toad forum.
You could make sure that statistics were collected after the database upgrade, but if that's not the problem, then you should talk to them about it.
My advice - reproduce and demonstrate the slowness to them using SQL*Plus. It's always best to take DB tools out of the equation. Also, if you mention Toad, it's possible that they will just say it's a Toad problem.