Characterset of Database

You can either check with your DBA or run the following SQL to determine whether your database character set is UTF-8. 

SELECT value$ FROM sys.props$ WHERE name = 'NLS_CHARACTERSET' ;

It should return the value AL32UTF8.

Another option is to run the following SQL :

SELECT * FROM NLS_DATABASE_PARAMETERS

The value against NLS_CHARACTERSET should be UTF8.