CDC synchronization - how to make it perform

Question

For synchronization between a transactional database and a data warehouse we've been using synchronous CDC. Performance is still somewhat an issue.
The situation is as follows (simplified):
EMP table. This is a large table (40 million + records) with a lot of mutations. The CDC log table contains about 3 million entries (records) each day, which are used to update the data warehouse. About 50% of the changes consists of updates.
The data of the describer view looks something like
operation$;empno;name
I;1;John
UU;1;John
UN;2;John
Since PK updates are allowed, all data manipulations needs to be processed to the data warehouse (to another EMP-like table). At this moment this is done via an old-fashioned for loop.
Since PK updates are allowed (and an additional functional identifier is not an option at this point in time) the mutations need to be processed sequential. Is there a faster 'bulk' option to do just this?

Answer 1

Maybe you can try something like this:
MERGE INTO emp e
   USING (SELECT   cep1.operation$, cep1.empno, cep1.NAME,
                   TO_NUMBER (NULL) chg_empno, TO_CHAR (NULL) chg_name
              FROM cdc_v_emp cep1
             WHERE cep1.operation$ = 'I'
          UNION ALL
          SELECT   cep2.operation$, cep1.empno, cep1.NAME, cep2.empno,
                   cep2.NAME
              FROM cdc_v_emp cep1, cdc_v_emp cep2
             WHERE cep1.cscn$ = cep2.cscn$
               AND cep1.rsid$ = cep2.rsid$
               AND cep1.operation$ = 'UU'
               AND cep2.operation$ = 'UN'
          ORDER BY cep1.cscn$, cep1.rsid$) c
   ON (e.empno = c.empno)
   WHEN MATCHED THEN
      UPDATE
         SET e.empno = c.chg_empno, e.NAME = c.chg_name
   WHEN NOT MATCHED THEN
      INSERT (e.empno, e.NAME)
      VALUES (c.empno, c.NAME);:)
PS: Note that I changed the order (and name) of some columns in the "USING" query.
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