There is a Oracle database with archivelog mode, and no backup. A tablespace is dropped, and how to recover?
Is there any old copy of the datafiles from the dropped tablespace. For example from a system backup or image?
If so, you may possibly be able to extract some of the data from the datafiles using Oracle DUL (search for it: Oracle Data Unload utility).
DBRECOVER Recovery Options
For Oracle incidents, start with the DBRECOVER for Oracle trial to verify table visibility, row previews, and export readiness on copied datafiles. For MySQL and InnoDB incidents, DBRECOVER for MySQL is free software and can inspect.ibd files, ibdata1, and database directories locally.
When the case is urgent, preserve the original files first, work from copies, and contact paid emergency support with the database version, platform, error messages, file list, and recovery objective.