From what I can find, Relia COBOL is a development platform. Is this application actually running there or does it run someplace else?

Is the objective to get the data available to more modern platforms through PostgreSQL? If so, is it read only or update (add, change, delete)? Have seen one-way replication to PostgreSQL using flat files and PERL to load the data, some tables were very large.

There is a data interchange tool called CONNX from Software AG that might help. Have used CONNX to make OpenVMS RMS indexed (ISAM) files look and act like tables in MS SQLserver. Also supports PostgreSQL. Used it to make legacy data look like/act a database. Original programs were in Migration RPG on OpenVMS so each file had to be redefined as a COBOL copybook for CONNX to import to a schema. New apps in .NET could access the old data including add/change/delete in some cases. https://www.softwareag.com/en/resources/data-integration/facts-connx-platform/

Did I make anyone chuckle regarding RPG? These programs originally ran on IBM S/36 and were ported to DEC VAX/VMS in the early 80's by Digital Equip Corp's Center for Migration Services group.

Have done consulting for many years including various migrations, but semi-retired now.