Oracle 11g accessing data in Oracle 7 I am working on a project that involves converting production data from an Oracle 7 DB to our system, which use Oracle 11g. In our other projects, we use DB link to access the other system DB, which is usually Oracle 10g. Can we have similar solution for Oracle 7? 

We need a solution that can minimize down time of system.
DB links are probably not going to work as a solution. Oracle7 is crazy old.

The question's facts are little limited. What types of objects (e.g., tables, stored procs, triggers, etc.) are involved? How much data? That said:

As it relates to table data, my solution would be to spool the data to text and access the text via external tables you setup in the 11g db.

In the 11g db, create the tables with the structure and referential integrity you require. It's been so long since I used Oracle7, so I don't think you can leverage DBMS_METADATA to obtain this DDL. You may have to get creative to reconstruct it.

Fill them with data as selects from the external tables.

Finally, index the new tables as desired.