How long to keep the backup and associated archived redo logs.
KEEP UNTIL TIME [=] 'date_string' [LOGS | NOLOGS] KEEP FOREVER [LOGS | NOLOGS] NOKEEP
Specifying LOGS will ensure that all the archived logs required to recover this backup (or copy ) will remain available for as long as the backup is available.
If you plan to restore and recover all data up until the current time then logs will be required.
For a point in time backup e.g. to keep a historical record then use NOLOGS.
NOLOGS is not valid if the backup is inconsistent.
"It's what you learn after you know it all that counts" - John Wooden
BACKUP - Back up database files, archive logs, backups, or copies.