set term ^;
execute block as
    declare x int;
begin
    for 
        execute statement ('select gen_id(g,1) from rdb$types,rdb$types,rdb$types')
        on external 
            rdb$get_context('SYSTEM','DB_NAME')
            as user 'SYSDBA' password 'masterkey'
        into x
    do begin
    end
end
^
set term ;^
rollback;

commit; 
set list on; 
select * from mon$statements 
where mon$attachment_id != current_connection; 
set count on; 
delete from mon$statements where mon$attachment_id != current_connection; 

Statement failed, SQLSTATE = 42000
Execute statement error at isc_dsql_fetch :
335544794 : operation was cancelled
Statement : select gen_id(g,1) from rdb$types,rdb$types,rdb$types
Data source : Firebird::C:\MIX\FIREBIRD\QA\FBT-REPO\TMP\E30.FDB

Statement failed, SQLSTATE = 42000
Execute statement error at isc_dsql_fetch :
335544794 : operation was cancelled
Statement : select gen_id(g,1) from rdb$types,rdb$types,rdb$types
Data source : Firebird::C:\MIX\FIREBIRD\QA\FBT-REPO\TMP\E30.FDB
-Execute statement error at isc_dsql_free_statement :
335544794 : operation was cancelled
Statement : select gen_id(g,1) from rdb$types,rdb$types,rdb$types
Data source : Firebird::C:\MIX\FIREBIRD\QA\FBT-REPO\TMP\E30.FDB