Hello, Fabiano!

Monday, May 21, 2012, 11:49:01 PM, you wrote:

F> I think Firebird uses the best approach for deleted records but I don't
F> understand much why.

real SQL server must have transaction control and conform to ACID
requirements. It can be done by different mechanisms - locking,
versioning, transaction log, etc. Firebird (and InterBase) uses one
mechanism, PostgreSQL - alike but different, MS SQL uses
transaction log even for versioning (as Oracle), etc.

F> In this aspect it is very different than Paradox that
F> rewrite the whole page without deleted records (if is not the first or last
F> record of the page).

Yep, Paradox is a locking file-server storage, it behaves differently.
At least, it have tree-structure of table, if it has primary key -
keys and pointers in .PX file, and sorted by PK data in .DB file.

F> Dmitry, I Just curious!
as I was in the beginning of 90th :-) Have fun!

--
Dmitry Kuzmenko, www.ib-aid.com