There are few ways to create a DBLINK:
Since the first two methods are covered in the technical documentation here: Install and Configure the Data Warehouse
Here we will cover the third one, how to create a DBLINK with a Clarity admin command
Release : Any
Component : CLARITY SAAS DATA WAREHOUSE
admin db create-db-link -Dtype=app -Dsysusername= -Dsyspassword=
For most cases just admin db create-db-link should work, but some environments will require the other parameters as well.
Reference: Load DWH job frequently reported issues