How TO troubleshoot ADM8010E Backup was unable to copy requested log file

During a recent review of backup failure exceptions this error message appeared:

SQL2428N The backup operation did not complete because an error was encountered while the backup utility was retrieving the log files.

The platform was DB2 LUW 10.1 on Red Hat Linux 6 integrated with the Avamar Plug in 7.1 .

The db2diag log file reported this error message at the same time:

ADM8010E Backup was unable to copy requested log file "0003456.LOG" for inclusion in the backup image. The backup has been aborted

The backup method used is ONLINE with INCLUDE LOGS. For a successful ONLINE BACKUP with INCLUDE LOGS   all active logs from the time of the ONLINE BACKUP starting  to the Online Backup record must be included .

How do you troubleshoot this error?

1. Verify if the log file is no longer active. Has the file been archived and subsequently been manipulated ? For example deleted , renamed, security path change
2. If during the ONLINE BACKUP the log file is archived . When the transaction log file is archived , the ONLINE BACKUP attempts to retrieve the file from the archive. If the file is not available in the archive , that is when the SQL2428N error appears.
3. You may find you can see the log file via the backup utility , but the ONLINE BACKUP cannot retrieve the file. Check the log on account has access to this file
4. DB2 LUW archival logging works by configuring LOGARCHMETH with the target archival logging method. DB2 LUW receives a message from LOGARCHMETH, which moves the active log into the archival logging path. Once the archival logging process completes, DB2 LUW no longer manages the file when it’s in the archival log. 
5. The key message is to explore the possibility of some sort of log file manipulation once it’s in the archival log. Some examples include archival logging clean up or deletion
6. Although generally true – there are various configurations in DB2 LUW and utilities , such as db2adutl (How to use Db2adutl delete logs (DBA DB2)) while allow a DBA to connect to TSM and delete files.