Connect two remote oracle databases as a schemas on each other

This Question is about Oracle Database.

I have two remote databases DB_1 and DB_2, and I have two schemas on each database: Schema DB_1 and Schema DB_2 on database DB_1, and Schema DB_1 and Schema DB_2 on database DB_2. I want to reach database DB_2 Schema DB_2 from database DB_1 Schema DB_1. For example: when I try this query in DB_1 from schema DB_1:

SELECT * FROM DB_2.example_table

I got an error because there is not table "example_table" in DB_2 Schema on the DB_1 database. But, when I try the same query on DB_2 Schema DB_2, I got the correct result (some data).

So, I need to tune my databases in some way so I can SELECT * FROM DB_2.example_TABLE from DB_1 Database.

But, there is another problem, I don’t have permission to CREATE LINK. However, when I query SELECT * FROM ALL_LINKS; on my production database DB_1 schema DB_1 – there are no links at all. So, I need to figure out which way my production Databases was linked (unfortunately my colleagues don’t know either). On my production database DB_1 schema DB_1 I can fetch data with the query:

SELECT * FROM DB_2.example_table

And the data I got is the same if I try to query the same on DB_2 production database DB_2 schema.

But there are no public\private Links on DB1/DB2 production databases at all. Is there another way to create a "connect" between my databases? (I queried SELECT * FROM ALL_LINKS from DB_1 schema DB_1, is this possible so I can fetch some other data if I try the query on DB_1 schema DB_2?)

Thanks in anticipation!