Hi Stefan,
Thanks for your reply. I found some points with your hint. Some summary for others:
460620 - Migrating archive files:
"Archived data may have to be migrated. One solution is to perform an SLO service archive migration. You can also perform an archive migration for archive files using the Archive Development Kit (ADK)."
153433 - Access to archived data from other logical systems
"For data security reasons, the ADK checks whether an archive file was created in the same system and client where it is to be read. If the client, system or file key do no longer correspond to the meta data that were valid at the time of archiving, you can no longer always access the archive file, particularly for reloading. If only the system ID changes when a new installation due to a system copy is carried out, read accesses are still possible. No solution is provided in the standard system. The access to archive files from other logical systems must be taken into account and carried out in a migration project."
Unfortunately, I still do not know if it is possible to read archived data outside of SAP.
Best Regards,
Jan