Subject Re: [firebird-support] Lock conversion denied
Author Ann W. Harrison
At 08:58 AM 11/3/2004, Bob Murdoch wrote:
> I found the following entry:
> page 2111936, page type 7 lock conversion denied (215)
>I can't find any reference to 'lock conversion denied' in any
>documents or newsgroup.
>Can anyone shed a little light on a definition and what this means as
>far as database health goes?

Not surprisingly, that's a lock manager error. Page type 7 indicates
an index page. When a transaction reads a database page, it gets a
protected read lock. To change a page, it must convert the lock to
exclusive write. If there are no other readers sharing the page, the
lock conversion is simple. If the page is shared, other users must
release the page before the conversion can happen. Sometimes they
can, sometimes they can't. This is a rare, but fatal error for the
transaction involved.

The comment in the code is:

/* Case: lock manager detected a deadlock, probably caused by locking the
bdb's in an unfortunate order. Nothing we can do about it, return the
error, and log it to firebird.log. */