We have a strange situation where we have Oracle 10, linked to Oracle 8, linked to Oracle 7. This is so we can keep an existing front end that only supports the Oracle 7 database, whilst developing a new one that only supports Oracle 10. What fun.

We got this error:

DatabaseError: ORA-04054: database link DBNAME.WORLD does not exist

This is the name of the link from Oracle 8 to Oracle 7.

We were confused as we could select from and describe the table used in the query that caused this, from Oracle 10.

The problem turned out to be that we were referencing columns in the table that didn't exist. Oracle was hiding the invalid column name error and just giving us this database link error.