SQL for Tunning task

Ref:
http://docs.oracle.com/cd/E11882_01/server.112/e25523/parallel006.htm
http://docs.oracle.com/cd/E11882_01/server.112/e16638/hintsref.htm
http://docs.oracle.com/cd/E14072_01/server.112/e10837/parallel.htm
http://docs.oracle.com/cd/E11882_01/server.112/e25523/parallel002.htm
Query to check parallel executions on instance:
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SELECT QCSID, SID, INST_ID "Inst", SERVER_GROUP "Group", SERVER_SET "Set",
  DEGREE "Degree", REQ_DEGREE "Req Degree"
FROM GV$PX_SESSION ORDER BY QCSID, QCINST_ID, SERVER_GROUP, SERVER_SET;

SELECT NAME, VALUE FROM GV$SYSSTAT
WHERE UPPER (NAME) LIKE '%PARALLEL OPERATIONS%'
OR UPPER (NAME) LIKE '%PARALLELIZED%' OR UPPER (NAME) LIKE '%PX%';

SELECT px.SID "SID", p.PID, p.SPID "SPID", px.INST_ID "Inst",
       px.SERVER_GROUP "Group", px.SERVER_SET "Set",
       px.DEGREE "Degree", px.REQ_DEGREE "Req Degree", w.event "Wait Event"
FROM GV$SESSION s, GV$PX_SESSION px, GV$PROCESS p, GV$SESSION_WAIT w
WHERE s.sid (+) = px.sid AND s.inst_id (+) = px.inst_id AND
      s.sid = w.sid (+) AND s.inst_id = w.inst_id (+) AND
      s.paddr = p.addr (+) AND s.inst_id = p.inst_id (+)
ORDER BY DECODE(px.QCINST_ID,  NULL, px.INST_ID,  px.QCINST_ID), px.QCSID,
DECODE(px.SERVER_GROUP, NULL, 0, px.SERVER_GROUP), px.SERVER_SET, px.INST_ID;

SELECT * from v$pq_sysstat;
SELECT * FROM v$px_process;
SELECT * FROM v$px_sesstat;
SELECT * FROM v$px_process_sysstat;


Examples
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ALTER TABLE table_name PARALLEL (DEGREE 8);
SELECT /*+PARALLEL(table_alias, degree, nodes)*/ *
  FROM table_name ...
OR
SELECT /*+PARALLEL */ * FROM table_name/View name ...