Switchover and failover using dgmgrl earlier in 11g, was able to provide an ample amount of information. But with 12c version Oracle introduced a new procedure validate database, which helps to provide DBA with lots of information related to pre- switchover/failover tasks.
Managed by Clusterware is added in 12cR2, which was not available in earlier 12CR1. Similarly Automatic Diagnostic
Repository Errors is removed in 12cR2 which was available earlier in 12cR1. Few more parameter are added, it's difficult to get into nitty-gritty details about each and every property. All in all great job done by Oracle savvy engineers to pinpoint specifics related to pre-switchover tasks.
I happen to test it and run it across 12.2.0.1.0 database.
Even though we do get a detailed information prior to hand before the switchover. Database alert log and dataguard alert log will come to rescue at the time of database switchover or failover task.
