Subject Re: [firebird-support] Very strange page type error raised during backup
Author Ann W. Harrison
Gabor Boros wrote:
> Hi,
> My colleague reported an error to me which raised during backup.
> database file appears corrupt
> wrong page type
> page 24 is of wrong type (expected 4, found 6)

Hmm... Interesting. Normally wrong page type errors involve
types 5 and 7, which are respectively data and index pages.
Vlad has fixed a bug or two that left pointers to index pages
that had been released and reused - often as data pages.
What you've got is an index root page that something expects
to be a pointer page.

Stranger is that the page number is 24. The first pages of
a database hold system table information and they're created
with the database. I think page 24 is normally a pointer page
for the RDB$FILES system table.

Did the error happen immediately after the backup started? Gbak
reads the system tables first, so if the error wasn't essentially
instantaneous, it had no business looking at page 24.

> I searched this message on the lists and the tracker.
> Found only one message about this error:
> I think this is not a database problem, because "page 24" reported too.

I agree that the problem is likely not to be in the stored
data, since both reports are for the same page, and both
were reported by gbak. But the error is in the server, not
in gbak. Gbak is a user-level utility that accesses the
database through a public API and doesn't read pages directly.

> We use FB 2.1.2 Embedded on Windows XP SP3 32bit. Database is small
> (10-20MB) and 5-10 new records added per day.

Best regards,