> When I tested about error cases, I unplug the computer's network

cable between client and server.

> Then I re-connect the computer's network cable. In some cases,

uncomplete transaction (or invalid

> sessions?) keeps the lock then I cannot delete the specific row.

(there is no reply to the Firebird).

Firebird doesn't use locks the way many other databases use locks.

I am guessing you are using a WAIT transaction.

>
> In this case, the only solution is restart Firebird?

Not true. The Operating System will eventually tell Firebird the
connection is broken. By default on Windows and Linux, this takes 2
hours. After that time, your second query will succeed. Look in
Firebird.conf for the information about this timeout and how to reduce it.

Is there any method to detect invalid (or

> uncomplete transaction) process and kill it like an Oracle's "ALTER

SYSTEM KILL SESSION".

>

No, but it would be useful.

Adam