Flávio Costa wrote:

> But how can I connect to database and be sure I'm the only one connect

SELECT from MON$ATTACHMENTS

> that everyone that try to connect after me will not succeed?

As already noted you can use gfix. Alternatively you could set up ON
CONNECT trigger that will throw an exception to other users if database
owner is connected (check in MON$ATTACHMENTS). Of course, in such
scenario you would only use the owner account to upgrade the metadata.

--
Milan Babuskov
http://www.flamerobin.org
http://www.guacosoft.com