CREATE DATABASE LINK TCS
CONNECT TO TCSDATA IDENTIFIED BY tcsdata
USING 'tcs'
/
I get the above mentioned loopback error when I run this.

CREATE DATABASE LINK valley_heart
CONNECT TO TCSDATA IDENTIFIED BY tcsdata
USING 'valley_heart'
/
It creates the db link but when I try to use it:
it gives me unable to resolve service name error.