Possible problem with exist backup and restore where there are errors in the dom.dbx
Willem van der Westhuizen <wavdwesthuizen <at> gmail.com>
2011-09-01 07:14:18 GMT
I want to report some issues with backup and restores for your
We have recently had two production databases that developed errors in
the dom.dbx (as reported in the report.log). The causes for these errors
were external, a hard drive filling up unexpectedly, and a problematic
xquery locking up the database repeatedly leading to forced shutdown and
restart sequences over a period of time. In both cases the backup /
restore functions partially failed.
We noticed that in the presence of these dom.dbx errors the backups
generated were becoming unreliable. Backups generated from the backup.sh
would exit prematurely, excluding large amounts of data, and backups
triggered through the user interface failed in two ways:
1. In one case it exited completely before finishing leaving an invalid
zip file. Fortunately, in this case the backup.sh backup worked
correctly and we could restore the database completely.
2. In the other case the data in the zip file was complete, but there
were inconsistencies in the __content__.xml file entries that would omit
all sub-collections of a particular name. In this case all
sub-collections with the name "workspace" were present in the data
backed up, but absent in the __content__.xml, hence not restoring when
we restored the database. There were another few sub-collection terms
that had the same problem. We were able to restore the database in the
end by creating restore shellscripts for each "workspace"
sub-collection, and restoring them individually. The bulk of the
database consist of collections for which the basic structure is
repeated. It seems to happen that if there is a dom.dbx corruption on
one of these sub-collections, all the other collection structures with
the same sub-collection is affected when creating the __content__.xml file.
It is always best to try and prevent dom.dbx errors. But it seems that
there might be some ways in which the backup and restore procedures
could be improved, particularly not to make the creation of the
__content__.xml dependent on the possibly broken indexes. Since the data
is still present, it should be possible to create the __content__.xml in
a way that would not be affected by index corruptions.
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