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

On Issuing of RMAN incremental backup, following error appears

RMAN-00571: ===========================================================

RMAN-00569: =============== ERROR MESSAGE STACK FOLLOWS ===============

RMAN-00571: ===========================================================

RMAN-03002: failure of backup command at 09/13/2016 01:07:19

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

ORA-19625: error identifying file /orabackup/arch/testdb_1_402813_745860807.arc

ORA-27037: unable to obtain file status

SVR4 Error: 2: No such file or directory

It may be possible that file would not be available physically. So please ensure file availability.

If already archive log files have been backed up then we can proceed for marking archive log files as expired and delete those file which is not required.But if archive log files have not been backed up then it would be better to take full database backup first to ensure full db recoverability and then we can do below activity -

RMAN> CROSSCHECK ARCHIVELOG ALL;

CROSSCHECK ARCHIVELOG ALL command will give information about expired RMAN repository and it will mark archive log file as expired who are not required or not available physically.

RMAN> DELETE EXPIRED ARCHIVELOG ALL;

DELETE EXPIRED ARCHIVELOG ALL command will delete all archive log files who was marked as expired using CROSSCHECK ARCHIVELOG ALL command.

Exact Steps That I followed to Solve 

1. First of all I copied above erroneous archive log file from archival backup

2. Run RMAN command on Oracle Server

   RMAN target /

3. On RMAN prompt, run the following command:

   RMAN> crosscheck archivelog all;

4. Now on RMAN prompt run below command

    RMAN> delete expired archivelog all;

5. Now I executed backup script and found that backup was successful.