RMAN retention policy - backup spfile and then redundancy = 5 removes it.

Question

I have a database that is Oracle Standard Edition and it is version 9.2.0.6.
The spfile has not changed since November, 2005. A list backup does not show an spfile backup with a tag of "hot_database_spfile_backup_full". I took a close look at the RMAN script log and was shocked to discover that the spfile backup from the current day is being deleted. Is that because of the redundancy = 5? I'm trying to figure out why a backup piece from the current day is being deleted?
Examples follow.
The script deletes obsolete with redundancy = 5, however, I believe the intent was to keep 25 days because one of the configure clauses is set to a recovery window of 25 days. I realize that the redundancy overrides the configure retention policy command. I can fix the script and remove the redundancy = 5.
In the RMAN run statement, I first resync the catalog, backup the spfile, a full backup of the database including current controlfile plus archive log (delete input), resync catalog, switch logfile, and backup any additional archive logs. The backup looks fine.
Then, I allocate a channel for maintenance type sbt. The script then has a "delete noprompt expired backup;" a "delete noprompt obsolete redundancy = 5;" and finally, a crosscheck;
example of backup piece that is later deleted:
Starting backup at 07/18/2006 20:00:14
channel t1: starting full datafile backupset
channel t1: specifying datafile(s) in backupset
including current SPFILE in backupset
channel t1: starting piece 1 at 07/18/2006 20:00:14
channel t1: finished piece 1 at 07/18/2006 20:00:15
piece handle=P*****_2338_1_596145614_FULL comment=API Version 2.0,MMS Version 5.2.0.0
channel t1: backup set complete, elapsed time: 00:00:01
Finished backup at 07/18/2006 20:00:15
deletion:
Deleting the following obsolete backups and copies:
Type Key Completion Time Filename/Handle
<other lines deleted>
Backup Set 27453 07/18/2006 20:00:14
Backup Piece 27454 07/18/2006 20:00:14
P*****_2338_1_596145614_FULL
deleted backup piece
backup piece handle=P*****_2338_1_596145614_FULL recid=2039 stamp=596145614
Deleted 12 objects
Why is a backup piece created on 7/18 being deleted in the maintenance step?
Thanks in advance!

Answer 1

In the next step in the script, the controlfile and spfile are backed up:
backup
full
skip inaccessible
tag hot_database_backup_full
format '%d_%s_%p_%t_FULL'
(Database
include current controlfile)
Plus Archivelog delete input;
Even though my backup script is redundant by backing up the spfile twice, when I list the backup of the spfile, I would have expected to find 5 backups with a tag of hot_database_spfile_backup_full and 5 with a tag of hot_database_backup_full. That is not the case. I only find spfiles with a tag of hot_database_backup_full. i am still perplexed by RMAN.
I will modify my script - remove the backup of the spfile, and crosscheck before the delete commands. I will also remove the redundancy = 5. The intent is to keep 25 days of backups.
Thanks for your comments