How to tune this query in Oracle 11g - sql

Question

I have been asked to tune the below query and would like to know if there is any better way to tune it?
SELECT req_dtl.lab_ord_occ_test_id ,
req_dtl.order_ref_no ,
req_dtl.accession_no ,
req_dtl.test_code ,
req_dtl.test_name ,
req_dtl.test_id ,
req_dtl.schedule_id ,
req_dtl.lab_ord_occ_id ,
req_dtl.order_type ,
lab_occ.facility_id ,
lab_occ.patient_id ,
lab_occ.order_draw_dt ,
hdr.source_system ,
(SELECT CORPORATION_ACRONYM
FROM corporation c,
facility f
WHERE c.corporation_id = f.corporation_id
AND f.facility_id = lab_occ.facility_id) AS corporation_acronym,
tst.container ,
lab_occ.order_duration_type ,
occ_test.mnc_yn
FROM ORDER_REQUISITION_HEADER hdr ,
ORDER_REQUISITION_DETAIL req_dtl ,
LAB_ORDER_OCC_TEST occ_test ,
LAB_ORDER_OCC lab_occ ,
TEST tst
WHERE hdr.requisition_hdr_id = in_requisition_hdr_id
AND hdr.msg_sent_to_lab_yn = 'Y'
AND req_dtl.requisition_hdr_id = hdr.requisition_hdr_id
AND occ_test.lab_order_occ_test_id = req_dtl.lab_ord_occ_test_id
AND req_dtl.test_id = tst.test_id
AND tst.accession_type NOT LIKE 'CMP%'
AND occ_test.status != 'R'
AND occ_test.lab_order_occ_id = lab_occ.lab_order_occ_id
AND lab_occ.status = 'A'
AND occ_test.created_dt >= hdr.msg_sent_to_lab_dt
AND NVL(occ_test.test_sent_to_lab_yn,'N') = 'N'
AND NOT EXISTS
(SELECT orddata.*
FROM MISSING_ORDER_DATA orddata,
TEST_CONFIG_HOLD_AOE tcha
WHERE orddata.test_id = tcha.test_id
AND tcha.active_yn = 'Y'
AND orddata.status_flag = 'A'
AND orddata.answer IS NULL
AND orddata.msg_sent_to_lab_yn = 'N'
AND orddata.lab_order_occ_test_id=occ_test.lab_order_occ_test_id
)
ORDER BY req_dtl.accession_no;
In the execution plan no tables are going for full table scan.Only nested loops are more.
*Suggest better way to tune this query *

Answer 1

AND NOT EXISTS
(SELECT orddata.*
FROM MISSING_ORDER_DATA orddata,
TEST_CONFIG_HOLD_AOE tcha
WHERE orddata.test_id = tcha.test_id
AND tcha.active_yn = 'Y'
AND orddata.status_flag = 'A'
AND orddata.answer IS NULL
AND orddata.msg_sent_to_lab_yn = 'N'
AND orddata.lab_order_occ_test_id=occ_test.lab_order_occ_test_id
)
could be moved to FROM
FROM
...
LEFT JOIN (SELECT DISTINCT orddata.lab_order_occ_test_id
FROM MISSING_ORDER_DATA orddata,
TEST_CONFIG_HOLD_AOE tcha
WHERE orddata.test_id = tcha.test_id
AND tcha.active_yn = 'Y'
AND orddata.status_flag = 'A'
AND orddata.answer IS NULL
AND orddata.msg_sent_to_lab_yn = 'N'
) missing ON missing.lab_order_occ_test_id = occ_test.lab_order_occ_test_id
WHERE missing.lab_order_occ_test_id IS NULL
Also you should move the acronym
FROM
...
INNER JOIN (SELECT CORPORATION_ACRONYM, f.facility_id
FROM corporation c,
facility f
WHERE c.corporation_id = f.corporation_id) acr ON
acr.facility_id = lab_occ.facility_id)

Answer 2

...Additionally, the TEST object must have an index on accession_type otherwise the tst.accession_type not like 'CMP%' clause will be slower than necessary.
Also, the clause: NVL(occ_test.test_sent_to_lab_yn,'N') = 'N' is essentially an outer join on partially-validated data. Does the test_sent_to_lab_yn column in occ_test contain nulls? If not, consider using an IN clause along with a valid list. [it looks like a yes/no column, maybe this should be equality on 'Y' and get someone to clean up the nulls?]
Please post the explain plan so we can suggest a re-ordering of the predicates in order to minimize the row-returns in first clause....and make HINT suggestions.