found this:
The following query recovers the equivalent values from the system tables. You can observe that the symbolic names are not exactly the same:

SQL> select rdb$type || '=' || rdb$type_name
CON> from rdb$types
CON> where rdb$field_name = 'RDB$MECHANISM';
======================================
0=BY_VALUE
1=BY_REFERENCE
2=BY_VMS_DESCRIPTOR
3=BY_ISC_DESCRIPTOR
4=BY_SCALAR_ARRAY_DESCRIPTOR

at

http://www.cvalde.net/document/using_descriptors_with_udfs.htm

This does not actually describe whether the system declaration asked for FREE_IT.

I cannot see a value in these tables that describe that.

Kind Regards,

Robert.