Soemtimes you need to check your cluster name on your RAC  instance. Here is the steps:

cd $ORA_CRS_HOME/bin
./cemutlo -h        <=== will list all the options
Usage: ./cemutlo.bin [-n] [-w]
where:
-n prints the cluster name
-w prints the clusterware version in the following format:
<major_version>:<minor_version>:<vendor_info>

./cemutlo -n
clustergp1    <=== cluster name, default cluster name is “crs”

Referance:
How to Query the Cluster Name [ID 577300.1]
How to manage DB Control 11.1.0.x for RAC Database with emca [ID 578011.1]