NVDB backups complete with warnings - "Backup xxx is incomplete. Required old streams are missing (94569)

NVDB backups complete successfully but return warnings.
The log may show the following messages:

Bad segment found
with context:
Segment: Segment is on media that should have been retired: Id 532449
Stream d30a02acb002764f8b7200002c10000001000000
From 850234376192 To 1067814944767
Job 7124 Instance 10 Phase 1
IP address 0xac020ad3 and 0xd30a02ac
Date 21:00 23 Mar 2012 and 07:04 21 Jun 2004

Warning Media Manager Segment Check: 17498 segments examined, 340 segments with no media, 0 orphaned segments, 0 discarded segments

Information 2012/06/26 11:17:37 91 Media NVSERVER Session with incomplete new streams: Backup 156794 Job 6940 Instance 28 Phase 1
Warning 2012/06/26 11:17:38 91 Media NVSERVER Backup 155702 is incomplete. Required old streams are missing
Information 2012/06/26 11:17:45 91 Media NVSERVER No Session matching Backup Index 292196

Although these warnings are informational and are returned by the database check performed during NVDB backups, all warnings should be reported to Quest Support
for validation and confirmation on the NVDB state.

In this particular instance, these warnings are normal as they have been introduced by a media scan of several old tapes.
During media scans, the backup indexes present on tape are imported into the MediaDatabase and kept for a default period of 7 days.
As the scans of old tapes are usually random, incomplete backup sets can be imported with missing segments and streams, as the tapes containing the missing segments have not yet been scanned.

In such context the MediaDatabase check during backup will detect that some imported backups are incomplete and report messages such as:
Bad segment, backup incomplete, session with incomplete new streams...

When NVDB backups show warnings pointing to incomplete backups or missing streams or bad segments,
investigate what media operations have occurred between the last known good NVDB backup and the one that started exhibiting the warnings.
Look for media scans and potential imports of old media into the database, as these will most of the time introduce incomplete backups for which missing segments are located on tapes that have not been scanned.

As these imported indexes are kept for 7 days by default, once they are retired these warnings should disappear.
If they do not disappear 7 days after the scans, please contact Quest Support for further investigations.