The instance prefix is invalid. Give a prefix with maximum 8 characters

Problem:

converting single instance database to RAC ONE node using RCONFIG gives error

-bash-4.2$ rconfig ConvertToRAC_AdminManaged_orcl.xml output_orcl.xml
<?xml version=”1.0″ ?>
<RConfig>
<Response>
<Result code=”1″ >
Got Exception
</Result>
<ErrorDetails>
The instance prefix is invalid. Give a prefix with maximum 8 characters.It may be different from SID of existing single-instance database.
</ErrorDetails>
</Response>
</RConfig>

Solution:

Provide instance prefix less then 8 character in rconfig xml file

<!–Instance Prefix tag is optional starting with 11.2. If left empty, it is derived from db_unique_name.–>
<n:InstancePrefix>orcl</n:InstancePrefix>

and run again

rconfig ConvertToRAC_AdminManaged_orcl.xml output_orcl.xml