Retention policy for manual attachments

Hello All

I have set up a content repository (file system storage) in our SAP system for manual attachments. The users can manually attach and retrieve documents from FB03 (for ex.).

Since these documents do not have a document number, doctype, link table and retention as we configure in OAC3, can someone explain me how can I configure retention for these manual attachments? I know that these documents are updated in the table SOOD.

Thanks

VK