On my system, building the list of tables on a schema with 61 tables result on a timeout after 480 seconds on an Oracle 12c database. The problem is that each call to get the list of foreign keys or indexes result in requests that take several seconds each.

The problem lies with requests on tables user_constraints and/or all_constraints. As an example, getting the list of foreign keys on a database that has no foreign key takes 5 seconds for each call (305 seconds total only for that part).