MERGE statement tuning

Question

Hi All
I have MERGE statment to peform update or insert operation.
I popluate about 1 million records using sqlldr to a staging table.
I have to compare the record exists in main table then update with values in staging table, or else insert the record in main table.
I am using Oracle Database 10g Enterprise Edition Release 10.1.0.2.0.
The problem is the execution of this statement takes more than 3 hours to complete. The volume of main table in 6 million records.
Please help how I can tune this query or process to make it work faster.
The query is as below
merge into t1
using (
     select /*+ INDEX(st1 c_PK) */
          * from st1
     where (c1)
     in (
     select /*+ INDEX(st1 c_PK) */
     max(c1) from st1 where c1 >= pStat and mo_id < pEnd
     group by c2
     )) t2
on (t1.c1 = t2.c1 and t1.c2=t2.c2)
when matched then
     update set
     c4 = t2.c4,
c5 = t2.c5,
-- all other columns here
when not matched then
     insert ( c1, c2, c3, c4 ... )
     values
     (t2.c1, t2.c2, t2.c3, t2.c4 ..);

Answer 1

Just as an after thought oracle 10g allows you to know place slaves on the tables themselves.Do you mean setting a default degree of parallelism on the table? Because this "place slaves on the tables" way of describing it is new to me.
Judging by the size of the one table I would assign 4 slaves to this. I don't think you have nearly enough information to judge this.
Between this and the temp group tablespace setup should help you a great deal.There seems to be a question mark over this also.