You might have a need to ship redo logs over the SQL*Net connection to a remote host.
This is usually done in data guard setups.
If you only want to send redo logs over the network, you must have a standby instance running to be able to receive the logs. Otherwise, you will get warnings.
But you won’t need it to have all datafiles!
Here’s something from the docs:
Archived redo log repository
This type of destination allows off-site archiving of redo data. An archive log repository is created by using a physical standby control file, starting the instance, and mounting the database. This database contains no datafiles and cannot be used for switchover or failover. This alternative is useful as a way of holding archived redo log files for a short period of time, perhaps a day, after which the log files can then be deleted. This avoids most of the storage and processing expense of another fully configured standby database.
Oracle recommends using an archived redo log repository for temporary storage of archived redo log files. This can be accomplished by configuring the repository destination for archiver-based transport (using the ARCH attribute on LOG_ARCHIVE_DEST_n parameter) in a Data Guard configuration running in maximum performance mode. For a no data loss environment, you should use a fully configured standby database using the LGWR, SYNC, and AFFIRM transport settings in a Data Guard configuration and running in either maximum protection mode or maximum availability mode.
This is a handy feature. It would be nice if only a listener would be enough, but no – you need to have a physical standby instance running!