How to check Instance is RAC enabled or not

This post will help full to know Instance is RAC enabled or Not.

SQL> show parameter CLUSTER_DATABASE;

NAME                                 TYPE        VALUE
--------------------------------------------------------------               
cluster_database                     boolean     TRUE
cluster_database_instances      integer       2

SQL> select * from v$active_instances;

INST_NUMBER   INST_NAME
---------------------------------------
  1                          R1
  2                          R2

Or  you can check in parameter file from $ORACLE_HOME/dbs

*.cluster_database=TRUE

If the cluster database set to "TRUE" instance is RAC is enabled.