Hi
Many of us know about catctl.pl script to upgrade the databases using parallel slave processes since 12c. Adding to that there is executable in $ORACLE_HOME/rdbms/bin called dbupgrade utility which in turn calls out catctl.pl.
There is little known feature which is emulation feature you can run with this utility or script. it displays on screen the same output that you see during an actual upgrade.
$ORACLE_HOME/rdbms/catctl.pl -E
You can read more from here https://docs.oracle.com/database/122/UPGRD/testing-upgraded-production-oracle-database.htm#UPGRD52882
-Thanks
Suresh
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