Thanks for help.
I'm now aware that psychical database file size does nothing to do
with actual amount of user data stored into the database.

Just one more question:
Any tip on how to implement database limit restriction on user?

Only solution I can think of is to place triggers on all tables, count
all records in all tables, and then prevent user to insert/modify more
data then he is allowed. But, this will be slow and not 100% accurate
because of possible ongoing transactions...


Thanks for any advice,

Branimir

--- In firebird-support@yahoogroups.com, Helen Borrie <helebor@...> wrote:
>
>
> >btrumba wrote:
> >>
> >> I want to LIMIT database size. One user is using database. E.g.: let
> >> say that user can only insert 100Mb of data into database.
>
> At 03:10 AM 19/12/2007, Woody wrote:
>
> >The problem with size is that it's not an indication of the actual
> >amount of data. Deletions only remove the record from view, not
from the
> >database file itself. That only happens when you backup and restore.
>
> Woody, that's not true. I think what you intended to say was that
deleting records does not reduce the size of the database file. Like
the back versions of updated records, those of deleted records are
garbage-collected once they become uninteresting.
>
> What btrumba needs to understand is that Firebird stores the older
versions of changed records and the deleted records for as long as it
takes to keep them available to other transactions that are interested
in them. The length of time that the back versions survive depends on
how long those other transactions take to lose interest in them.
>
> Once a back version becomes uninteresting, the disk space it has
used becomes available for re-use. Backing up the database and
replacing it with a restored version gives you a freshly laid-out
database with no spare pages.
>
> Perhaps btrumba does not know that a Firebird database file is not a
folder full of hidden physical files storing physical tables of data
and indexes, like Access and some other desktop databases. It is a
single logical file containing data laid down in a compressed format
on chunks of disk that are controlled by the Firebird engine. These
chunks are known as "pages". As Ann explained, there are many types
of pages, apart from data pages. For example, there are index pages
that store the node structures of the indexes, cascading pointer pages
for index and data pages, pages for storing BLOBs, there's a page to
store transaction inventory, and so on.
>
> So, while you could calculate the actual size of data by counting
bytes across the row structure and multiplying that by the number of
rows that are visible to a particular transaction, that does not tell
you anything about the size of the database itself.
>
> It is not uncommon for databases containing relatively small amounts
of "actual data" to be bloated to 2 or 3 times their minimum size due
to badly written applications that prevent the Firebird engine from
identifying and removing obsolete back versions.
>
> ./heLen
>