Oracle: Inserting data using a database link
If you want to have a database link on DB1 that points to DB2, DB1 would need to be able to resolve whatever TNS alias you specify in the database link definition.  Assuming that you are using tnsnames.ora files everywhere for TNS name resolution, that would mean that the tnsnames.ora file on DB1 would need to have an entry that points to DB2.  The TNS alias you specify in your CREATE DATABASE LINK statement would need to reference that TNS alias (which could be different than the alias for DB2 that you have created on your local machine).  If you have limited access to the machine where DB1 resides, you would most likely need the DBA for DB1 to ensure that the TNS alias gets created appropriately.