How to monitor parallel processing

Question

Hi All,
I have 2 short questions:
1. When we want parallel processing, we can either use a parallel hing in the query, or alter a table to be parrallel. My question is what is the difference in the following 2 syntax:
a. ALTER TABLE myTable PARALLEL (DEGREE 3);
b. ALTER TABLE myTable PARALLEL 3;
Does the "DEGREE" keywor make any difference? or they both are same statements?
2. When we enable parallel processing, how can we monitor oracle processes, to confirm that a certain table is being actually processed by multiple threads of a singe user process?
An early response would be highly appreciated. Thanks.

Answer 1

user566817 wrote:
2. When we enable parallel processing, how can we monitor oracle processes, to confirm that a certain table is being actually processed by multiple threads of a singe user process?There are a number of virtual performance views that can be used. Please refer to the Oracle® Database Reference guide for details on these.
Had a look though my scripts and I have this one.. cannot recall if I "borrowed" it from somewhere and customised it and how old it is.. but it should (hopefully) still be mostly correct. It uses the virtual view v$px_process to determine the list of current PQ slaves in the pool and if they are used, map them to the Oracle session using them.
select  distinct
        x.server_name           as "PQ",
        x.status                as "Status",
        x.sid                   as "OraPID",
        w2.sid                  as "Parent OraPID",
        v.osuser                as "O/S User",
        v.schemaname            as "User",
        w1.event                as "Child Wait",
        w2.event                as "Parent Wait"
from    v$px_process    x,
        v$lock          l,
        v$session       v,
        v$session_wait w1,
        v$session_wait w2
where   x.sid =! l.sid(+)
and     to_number (substr(x.server_name,3)) = l.id2(+)
and     x.sid = w1.sid(+)
and     l.sid = w2.sid(+)
and     x.sid = v.sid(+)
and     nvl(l.type,'PS') = 'PS'Use at own risk - best would be to verify that this is still valid using the Reference Guide. Or create similar ones using the available V$ views for the details you want to see (e.g. SQL statement executed per PQ, etc).