To check if the Database is configured with Cluster. 

NAME                VALUE
------------------- -------------------
cluster_database    TRUE

SQL>
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To check active DB status with RAC's instance name along with connected server:-

  INST_ID INST_NUMBER INST_NAME                                    CON_ID
---------- ----------- ---------------------------------------- ----------
         1           1 DBsGuru-rac1.world:dev12c1                  0
	 2           2 DBsGuru-rac2.world:dev12c2                  0

SQL>
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