Database Reference
In-Depth Information
oracle 18522 1 0 10:13 ? 00:00:00 ora_p002_ORA12CR1
oracle 18524 1 0 10:13 ? 00:00:00 ora_p003_ORA12CR1
oracle 18526 1 0 10:13 ? 00:00:00 ora_p004_ORA12CR1
...
prior to oracle 12
c
, if you hadn't modified the value of
PARALLEL_MIN_SERVERS
from the default of 0, you wouldn't
initially see any parallel execution server processes when you first started your instance. these processes
appeared after you ran a statement that processed in parallel.
If we are curious enough to want to watch parallel query, we can easily do so using two sessions. In the session
that we will run the parallel query in, we'll start by determining our SID:
EODA@ORA12CR1> select sid from v$mystat where rownum = 1;
SID
----------
258
In another session, we get this query ready to run (but don't run it yet, just type it in!):
EODA@ORA12CR1> select sid, qcsid, server#, degree
2 from v$px_session
3 where qcsid = 258
Now, going back to the original session that we queried the
SID
from, we'll start the parallel query. In the session
with the query setup, we can run it now and see output similar to this:
4 /
SID QCSID SERVER# DEGREE
---------- ---------- ---------- ----------
26 258 1 8
102 258 2 8
177 258 3 8
267 258 4 8
23 258 5 8
94 258 6 8
169 258 7 8
12 258 8 8
258 258
9 rows selected.
We see here that our parallel query session (
SID=258
) is the query coordinator SID (QCSID) for nine rows in this
dynamic performance view. Our session is
coordinating
or controlling these parallel query resources now. We can
