DBML (Database Markup Language) (see https://www.dbml.org/) is an open-source DSL language designed to define and document database schemas and structures. It is designed to be simple, consistent and highly-readable.
When you have an existing database an want to be able to represent it as DBML, you have different choices.
DBML offers tools themselves to convert SQL to DBML (see https://www.dbml.org/cli/ and https://www.dbml.org/js-module/).
But this repository additionaly offers an SQL script, so you have another option. That means, generating a DBML representation of your Oracle database via SQL.
This is a really simple script, but might help as a starting point. For us it does it's job very good...
We tested the results with https://dbdiagram.io/ and also generated a documentation website with https://dbdocs.io/.