Subject Re: [firebird-support] Re: Permission problem
Author Ann W. Harrison
Adam wrote:

> Worse still, and although I can not understand how it is possible,
> there have been reports about the source database being corrupted by
> copying it using a file system level copy utility.

Consider this case: you store a record in a table with an index.
The database has to add a page to the table to hold the new record.
To do so, it changes a page information page to show that the page
is now in use, and makes an entry on a pointer page for the table
that indicates that the page belong to the table. Then a new
entry is made in the index. Both the pointer page and page
information page occur before the new data page and the index
page in the data file.

To maintain on-disk consistency, the page are written in this
order: page information page, data page, pointer page, index
page. If your copy is unfortunate and gets the old versions
of the page information page and the pointer page but the new
versions of the index and data pages, an lookup that should
return the new record will get a corruption error of something
like "page 0 wrong type, expected 5 encountered 1". Zero is
the value set in empty slots on a pointer page.

In short, don't copy a running database.