RMAN-06059: expected archived log not found, lost of archived log compromises recoverability

RMAN attempted to backup an archive log file, but couldn't find it.

This can happen for a variety of reasons; the file has been manually moved or deleted, the archive log destination has recently been changed, the file has been compressed, etc.

Starting backup
current log archived
released channel: t1
RMAN-00571: ===========================================================
RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============
RMAN-00571: ===========================================================
RMAN-03002: failure of backup command at 14:24:55
RMAN-06059: expected archived log not found, lost of archived log
compromises recoverability
ORA-19625: error identifying file /u06/omr/oradata/arch/omr_1_22171_686671135.arc
ORA-27037: unable to obtain file status
Linux Error: 2: No such file or directory
Additional information: 3

Your options are either to restore the missing file(s), or to perform a crosscheck. To perform a crosscheck, run the following command from within RMAN:

RMAN> change archivelog all crosscheck;

Crosschecked 178 objects

RMAN> backup archivelog all;

input archive log thread=1 sequence=22177 recid=21267 stamp=800555057
input archive log thread=1 sequence=22178 recid=21268 stamp=800556249
channel ORA_DISK_1: starting piece 1 at 28-NOV-12
channel ORA_DISK_1: finished piece 1 at 28-NOV-12
piece handle=/u01/app/oracle/flash_recovery_area/OMR/backupset/2012_11_28/o1_mf_annnn_TAG20121128T164411_8cdxwxk3_.bkp tag=TAG20121128T164411 comment=NONE
channel ORA_DISK_1: backup set complete, elapsed time: 00:00:46
Finished backup at 28-NOV-12

Starting Control File and SPFILE Autobackup at 28-NOV-12
piece handle=/zone/catdb/backup/auto_cntrl_c-1333713947-20121128-05 comment=NONE
Finished Control File and SPFILE Autobackup at 28-NOV-12

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It is advisable to perform a full backup of the database at this point.

When an archive log crosscheck is performed, RMAN checks each archive log in turn to make sure that it exists on disk (or tape). Those that are missing are marked as unavailable. If you have got missing logs, this won't bring them back. It will allow you to get past this error and back-up the database though.