Roman Rokytskyy escreveu:

>>> Don't you need to update main database file to put a "label" that
>>> database is in "nbak"-like mode? I guess some more functionality is
>>> needed...
>>>
>> Yes, but the database may be burned to CD already locked. The
>> application will need to be installed on a fixed path.
>>
>> What I don't know is if the engine will open the file on the CD
>> (read-only) and the delta in read-write mode.
>>
>
> So, in fact we have two requirements:
>
> a) allow opening delta-file in read-write mode even if main database is
> opened in read-only mode;
>

Better thing:
- if main file can't be opened, try open in read-only mode.
- if open succeed and the file is locked, continue

> b) allow specifying a custom path for deltas in the firebird.conf file.
>
> The only drawback of this scheme is that there are no chances of
> nbak-ing the delta with nbak. But I think this is quite acceptable for
> this use case, since we're talking about embedded use where main
> database is bigger than delta.
>

I know some very interesting features that could be done (easily) with
NBAK. The problem is the understandable NBAK code. :-)

For example:
- replication
- flash back queries
- faster incremental backups
- database "branches" - database with various independent delta files -
very useful for group of people developing/testing on one copy of big
production database without interfering with others

> BTW, what about garbage collection in the delta?

Don't know.

--
Adriano dos Santos Fernandes
http://www.firebirdsql.org