Corrupted unread list in Mail database caused "This database cannot be read due to an invalid on disk structure"

Hi

I believe every IBM Domino administrator worked on issues related to invalid structure of Notes database.
Sooner or later it happened.

There are many reasons, why it may happen:
- issues with Antivirus/Anti-spam/Backup software
- different issues with Richtext/MIME items
- issues with DXL export/import
- issues with missing NLO-files
- ....other reasons .....

Today I resolved such issue for a mail database.
It was caused by corrupted note with unread list.
I performed following steps:


At first I tried to do copy-style compacting with removing view indexes

> load compact -c -d mail\aar.nsf
17.07.2014 11:43:52   Informational, database design compression is enabled in database mail\aar.nsf.
17.07.2014 11:43:52   Informational, document data compression is enabled in database mail\aar.nsf.
17.07.2014 11:43:52   Informational, DAOS is enabled in database mail\aar.nsf.
17.07.2014 11:43:52   Informational, LZ1 is enabled in database mail\aar.nsf.
17.07.2014 11:43:52   Compacting mail\aar.nsf (<username>),  -c -d mail\aar.nsf
17.07.2014 11:44:01   Error compacting mail\aar.nsf,  -c -d mail\aar.nsf: This database cannot be read due to an invalid on disk structure
17.07.2014 11:44:02   Database compactor process shutdown 

Then I tried 'fixup' with different parameters but nothing helped until I tried parameter -D that had to remove everything corrupted. I saw such message in console:

> load fixup -j -D mail\aar.nsf
17.07.2014 11:45:16   Database Fixup: Started:  -j -D mail\aar.nsf
17.07.2014 11:45:16   Performing consistency check on mail\aar.nsf...
17.07.2014 11:45:17   Unread log for user Unavailable in database g:\lotus\domino\data\mail\aar.nsf is being reallocated. ReasonCode:71
17.07.2014 11:45:17   Unread list for user <username> in database g:\lotus\domino\data\mail\aar.nsf is damaged and has been deleted: Release 9.0.1FP1|April  03, 2014
17.07.2014 11:45:18   Recovery Manager: Assigning new DBIID for g:\lotus\domino\data\mail\aar.nsf (need new backup for media recovery).
17.07.2014 11:45:18   Completed consistency check on mail\aar.nsf
17.07.2014 11:45:18   Performing consistency check on views in database mail\aar.nsf
17.07.2014 11:45:18   Informational, rebuilding view - user specified REBUILD (reading g:\lotus\domino\data\mail\aar.nsf default design note Title:'')
17.07.2014 11:45:19   Informational, rebuild view needed - collection object was deleted (reading g:\lotus\domino\data\mail\aar.nsf view note Title:'($SoftDeletions)|($SoftDeletion')
17.07.2014 11:45:19   Completed consistency check on views in database mail\aar.nsf
17.07.2014 11:45:19   Database Fixup: Shutdown

After that I run 'compact' again and that time it worked without any problems.
Issue was resolved.