This is the outcome of querying RDB$MECHANISM.
How do I know which one means FREE_IT?

SELECT RDB$MECHANISM,COUNT(*)
FROM RDB$FUNCTION_ARGUMENTS
GROUP BY RDB$MECHANISM

RDB$MECHANISM COUNT
============= =====
-1 3
0 20
1 56
3 2
5 5

BTW I have never used FREE_IT before and if
FREE_IT equals "1" then the database must be allocating this by default. Is this true?

How can I find out the meanings of the values in this field?

Kind Regards,

Robert.