> Is it possible to print message from Firebird SP (something like

dbms_output.put_line in Oracle)?

Well there is no official console window for Firebird, but there are a
number of ways to do something similar. At the simplest level, a
selectable stored procedure returns a row every time you call suspend,
so that may be 'enough' for what you want to do.

Otherwise, Firebird supports external functions which can do whatever
you want them to do. Our custom UDF library has a function that sends
a string to OutputDebugString, so we can send strings to any Windows
debugger.

Adam