What is the difference between expired and obsolete backups in RMAN?

When REPORT OBSOLETE or DELETE OBSOLETE determines, based on the user-defined retention policy, that a backup is not required for recovery, it is considered to be obsolete.When RMAN runs a crosscheck and is unable to locate the file, the backup is only then deemed to be expired.To put it simply, obsolete refers to “not needed,” whereas expired refers to “not found.”