If you specify DELETE INPUT (without ALL), then RMAN deletes only the copy that it backs up.
If you specify ALL, then RMAN deletes all copies of the specified logs that it finds in the V$ARCHIVED_LOG view.
The BACKUP ... DELETE INPUT command can delete archived redo logs, datafile copies, and backup sets after backing them up. This functionality is especially useful when backing up archived logs on disk to tape. RMAN backs up one and only one copy of each log sequence number, and then deletes the file that it backs up. For example, assume that you issue:
BACKUP ARCHIVELOG ALL DELETE INPUT;
In this command, RMAN backs up one copy of each log for each available sequence number, and then deletes only the file that it actually backs up.
If you specify the DELETE ALL INPUT option, then RMAN deletes whichever files match the criteria that you specify, even if there are several files of the same log sequence number. For example, assume that you archive to 3 different directories. Then, you issue this command:
BACKUP ARCHIVELOG ALL FROM SEQUENCE 1200 DELETE ALL INPUT;
In this case, RMAN backs up only one copy of each log sequence between 1200 and the most recent sequence, but deletes all logs with these sequence numbers contained in the three archive destinations.
The archived log failover feature means that RMAN searches every enabled archiving destination for good copies of a log sequence number. For example, assume that /log1 and /log2 are the only enabled archiving destinations, and that they contain the same sequence number. You run this command:
BACKUP ARCHIVELOG FROM SEQUENCE 123 DELETE ALL INPUT;
RMAN can start reading from any enabled archiving directory. For example, assume RMAN starts in directory /log1 and finds log_123.f there. Then, if RMAN discovers that log_124.f is corrupt, it searches in /log2 for a good copy of this log. Because DELETE ALL INPUT is specified, RMAN deletes all copies of logs on disk of sequence 123 and higher.