XCP - stderr log & delete copy id

1. why the  stderr log file hasn't been create under log dir ,even though  the path appers at the ini file ?

2. how can i delete  id of a copy , i want to use the name of the volume as id  so i ran  xcp copy -newid vol1  /source /dest 

and  i want to delete the id and use  it again for another path. 

Thanks