Oracle Insert Running longer!

Hi Expert,

I have below insert which took longer in production Machine. Sometimes it got stuck. Please help me on this.

I used to kill and re run the job but the query  stuck at the same insert query. I checked the "select" and found that there isn’t any record being pulled by the sub query so ideally it is inserting 0 records then also the query is stuck. Not sure why it is running longer.

/*INSERTING INTO SLS_ERROR WHEN THE QTY_ACT IS LESS THAN 0 */
INSERT /*+ append */ INTO STSC.SLS_ERROR
        (DMDUNIT
        ,DMDGROUP
        ,RIN_LOC
        ,DLV_LOC
        ,SLS_DAT_SRC
        ,SLS_TRS_TYP
        ,ZIP_CD
        ,MDS_STS
        ,TRS_DT
        ,WK_STA_DT
        ,QTY_ACT
        ,QTY_LST
        ,QTY_USR
        ,QTY_LIFT
        ,SLL_AMT
        ,SLS_AGG_MTD
        ,ON_PROMO_FL
        ,SCM_IND
       ,ROW_CRT_DT
        ,ROW_LST_UPD_SRC
        ,ROW_LST_UPD_DT
        ,ERROR_CD
        ,ERROR_TS
        ,STEP_NO
        ,ERROR_DESCR)
--  added use_nl hint because for some reason Oracle chose to do hash join with SH table first and taking nearly 20 hours to complete.
SELECT /*+ index(sh) use_nl(sh) */ -- 3/22/12 PawelS - changed hint to index(sh) because of limiting records to only those from SLS_WRK
        DMDUNIT
        ,DMDGROUP
        ,RIN_LOC
        ,DLV_LOC
        ,SLS_DAT_SRC
        ,SLS_TRS_TYP
        ,ZIP_CD
        ,MDS_STS
        ,TRS_DT
        ,WK_STA_DT
        ,QTY_ACT
        ,QTY_LST
        ,QTY_USR
        ,QTY_LIFT
        ,SLL_AMT
        ,SLS_AGG_MTD
        ,ON_PROMO_FL
        ,SCM_IND
       ,ROW_CRT_DT
        ,ROW_LST_UPD_SRC
        ,SYSDATE
        ,200
        ,SYSDATE
        ,80
        ,'ZERO OR NEGATIVE QUANTITY'
        -- - added alias sh for the hint above to work
FROM STSC.UDT_SLS_HIST sh
WHERE ROW_LST_UPD_SRC='HFMADJ'
AND QTY_ACT<=0
--  - added limiting the search to records from SLS_WRK
AND (DMDUNIT, RIN_LOC, DLV_LOC, MDS_STS, SLS_TRS_TYP, ZIP_CD, TRS_DT, SCM_IND, SLS_DAT_SRC) IN
                (SELECT /*+ PARALLEL(SW,18) FULL(SW) */
                        DMDUNIT, RIN_LOC, DLV_LOC, MDS_STS, SLS_TRS_TYP, ZIP_CD, TRS_DT, SCM_IND, SLS_DAT_SRC
                 FROM STSC.SLS_WRK SW);

Please let me know if you need more info.

Thanks!