Can't "stop" data pump job via dbms_datapump

Question

DBMS_DATAPUMP.101
I have a job I have OPENd, but never started. How do I get rid of it?
SQL> declare
2 v_handle number;
3
4 begin
5
6 v_handle := DBMS_DATAPUMP.ATTACH('RefreshFromDev','SYSTEM')
7 DBMS_DATAPUMP.STOP_JOB(v_handle );
8
9 end;
10 /
declare
ERROR at line 1:
ORA-31626: job does not exist
ORA-06512: at "SYS.DBMS_SYS_ERROR", line 79
ORA-06512: at "SYS.DBMS_DATAPUMP", line 911
ORA-06512: at "SYS.DBMS_DATAPUMP", line 3279
ORA-06512: at line 6
SQL> SELECT JOB_NAME, OWNER_NAME , STATE FROM DBA_DATAPUMP_JOBS;
JOB_NAME
OWNER_NAME
STATE
RefreshFromDev
SYSTEM
DEFINING
Obviously the job exists. I've tried issuing another Open with the same name and It complains that the job already exists. As I understand it, I have to attach to the job and issue a stop_iob in order to dispose of it.
Thanks
Steve

Answer 1

OK, mystery solved, sort of. If I close my sqlplus session, and log in again, issuing the same sql, it works.
I suppose I should read the message "job does not exist" as something like "already attached to a job, detach or disconnect"
Can anyone shed some light on this? I guess it means you can only attach to one job per session, or that only one handle can be issued per job per session. But I'm only guessing.
Thanks,
Steve