procedure TForm1.Button1Click(Sender: TObject);
var tb: TDBISAMTable;
begin
  tb:=TDBISAMTable.Create(nil);
  tb.databaseName:='C:\';
  tb.tableName:='table1';
  tb.open;
  tb.insert;
  tb.FieldByName('str').asString:='test';
  tb.Close;
  tb.Free;
// record is posted
end;

procedure TForm1.Button2Click(Sender: TObject);
var tb: TDBISAMTable;
begin
  tb:=TDBISAMTable.Create(nil);
  tb.databaseName:='C:\';
  tb.tableName:='table1';
  tb.open;
  tb.insert;
  tb.FieldByName('str').asString:='test';
//  tb.Close;
  tb.Free;
// record is NOT posted
end;