Effectively in both situations stand by becomes primary main distinction is when failover happens it indicates there is a problem at primary website in someway primary is not available either DB has unsuccessful or system at primary website. On other hand switchover is part of schedule action to make sure that DR is efficient.
Switching over refers to the operation of interchanging roles. This can be done multiple times back and forth between the different dbs.
Failover refers to the operation of delegating the primary role to one of the available standby databases because the primary is not available anyore. You won't do this if the primary is still available since it's kind of cutting the old primary off your Dataguard. This operation cannot be undone as the switchover.
Switchover is pre-planned activity. When there is planned outage of primary database or primary server. The stand-by database/server performs the primary role in this case. All functionality used to perform by it during outage.
When the primary database/server is not working that time failover occurs. That time stand-by stand-by database is converted to primary database. When there is server failure that time this occurs.
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