Why can I not validate by backup?

Question

Why can I not validate by backup.
The archive file was backed up to tape.
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
BACKUP VALIDATE DATABASE ARCHIVELOG ALL;
Starting backup at 14-SEP-06
using channel ORA_SBT_TAPE_1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS
RMAN-00571: ======================================================
RMAN-03002: failure of backup command at 09/14/2006 13:50:18
RMAN-06059: expected archived log not found, lost of archived log compromises recoverability
ORA-19625: error identifying file /oracle/XSQ/oraarch/XSQarch1_1343.dbf
ORA-27037: unable to obtain file status
HP-UX Error: 2: No such file or directory
Additional information: 3
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
RMAN> list backup of archivelog sequence 1343;
List of Backup Sets
===================
BS Key Size Device Type Elapsed Time Completion Time
11 7M SBT_TAPE 00:02:51 08-SEP-06
BP Key: 11 Status: AVAILABLE Tag: ADTLMWWN
Piece Name: XSQ_adtlmwwn.12_1
List of Archived Logs in backup set 11
Thrd Seq Low SCN Low Time Next SCN Next Time
1 1343 30237006 08-SEP-06 30243649 08-SEP-06
BS Key Size Device Type Elapsed Time Completion Time
14 7M SBT_TAPE 00:04:06 08-SEP-06
BP Key: 12 Status: AVAILABLE Tag: ADTLNWBH
Piece Name: XSQ_adtlnwbh.14_1
List of Archived Logs in backup set 14
Thrd Seq Low SCN Low Time Next SCN Next Time
1 1343 30237006 08-SEP-06 30243649 08-SEP-06
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
RMAN> REPORT NEED BACKUP;
RMAN retention policy will be applied to the command
RMAN retention policy is set to recovery window of 31 days
Report of files whose recovery needs more than 31 days of archived logs
File Days Name
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
RMAN> REPORT UNRECOVERABLE;
Report of files that need backup due to unrecoverable operations
File Type of Backup Required Name
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Answer 1

I ran crosscheck.
Than I ran this LIST BACKUP OF ARCHIVELOG SEQUENCE 1343;
List of Backup Sets
===================
BS Key Size Device Type Elapsed Time Completion Time
11 7M SBT_TAPE 00:02:51 08-SEP-06
BP Key: 11 Status: EXPIRED Tag: ADTLMWWN
Piece Name: XSQ_adtlmwwn.12_1
List of Archived Logs in backup set 11
Thrd Seq Low SCN Low Time Next SCN Next Time
1 1343 30237006 08-SEP-06 30243649 08-SEP-06
BS Key Size Device Type Elapsed Time Completion Time
14 7M SBT_TAPE 00:04:06 08-SEP-06
BP Key: 12 Status: EXPIRED Tag: ADTLNWBH
Piece Name: XSQ_adtlnwbh.14_1
List of Archived Logs in backup set 14
Thrd Seq Low SCN Low Time Next SCN Next Time
1 1343 30237006 08-SEP-06 30243649 08-SEP-06
Than I ran RMAN> BACKUP VALIDATE DATABASE ARCHIVELOG ALL;
Starting backup at 15-SEP-06
allocated channel: ORA_SBT_TAPE_1
channel ORA_SBT_TAPE_1: sid=17 devtype=SBT_TAPE
channel ORA_SBT_TAPE_1: VERITAS NetBackup for Oracle - Release 6.0 (2006031019)
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of backup command at 09/15/2006 09:23:31
RMAN-06059: expected archived log not found, lost of archived log compromises recoverability
ORA-19625: error identifying file /oracle/XSQ/oraarch/XSQarch1_1343.dbf
ORA-27037: unable to obtain file status
HP-UX Error: 2: No such file or directory
Additional information: 3