MERGE statement not working with use of hints

The following code has been written under Oracle 10g R2.

The first merge statement
will insert rows into the stg_provider table. However, if any hint at all is used
nothing will be written. I have other procedures using merge statements with hints
which work just fine. Any suggestions on where I should look would be appreciated.

    MERGE INTO stg_provider a

      USING TABLE( load_stg_provider() ) b
         ON (
                  a.prpr_id             = b.prpr_id
              AND a.effective_date      = b.effective_date
              AND a.terminated_date     = b.terminated_date
              AND a.sys_contract_mbr    = b.sys_contract_mbr
              AND a.mbr_contrived_key   = b.mbr_contrived_key
              AND a.subscriber          = b.subscriber
              AND a.suffix              = b.suffix
              AND a.elig_class_prod_cat = b.elig_class_prod_cat
             )

    WHEN NOT MATCHED THEN

      INSERT


       (

         prpr_id,
         effective_date,
         terminated_date,
         sys_contract_mbr,
         mbr_contrived_key,
         subscriber,
         suffix,
         elig_class_prod_cat
        )
      VALUES


       (

         b.prpr_id,
         b.effective_date,
         b.terminated_date,
         b.sys_contract_mbr,
         b.mbr_contrived_key,
         b.subscriber,
         b.suffix,
         b.elig_class_prod_cat
        );

    COMMIT; ==
  Merge statement with hint which doesn't write anything. ==

    MERGE /*+ APPEND */ INTO stg_provider a

      USING TABLE( load_stg_provider() ) b
         ON (
                  a.prpr_id             = b.prpr_id
              AND a.effective_date      = b.effective_date
              AND a.terminated_date     = b.terminated_date
              AND a.sys_contract_mbr    = b.sys_contract_mbr
              AND a.mbr_contrived_key   = b.mbr_contrived_key
              AND a.subscriber          = b.subscriber
              AND a.suffix              = b.suffix
              AND a.elig_class_prod_cat = b.elig_class_prod_cat
             )

    WHEN NOT MATCHED THEN

      INSERT


       (

         prpr_id,
         effective_date,
         terminated_date,
         sys_contract_mbr,
         mbr_contrived_key,
         subscriber,
         suffix,
         elig_class_prod_cat
        )
      VALUES


       (

         b.prpr_id,
         b.effective_date,
         b.terminated_date,
         b.sys_contract_mbr,
         b.mbr_contrived_key,
         b.subscriber,
         b.suffix,
         b.elig_class_prod_cat
        );

    COMMIT; Received on Thu Dec 07 2006 - 19:27:49 CST