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Before running the Graceful switchover check if there are any services running the database if so you might have to set the value of the DDC variable SERVICE_USED and SERVICE_USED_DR to Y. Check the usage of the variable in the below documentation link. DDC File Reference
If RMAN is used in no-catalog mode on primary or standby database, execution of Graceful Switchover will render any backup information and setting in primary and standby controlfiles unusable. After Graceful switchover, crosscheck and catalog of existing backups must be performed.
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