update tuning

Hello

I am trying to tune the following SQL

update TABLE A set (set col1, col2, col3) =

(select col1, col2 col3 from TABLE b where a.colA = b.colA and a.colB = b.colB  and b.col10=X);

TABLE has about 20 mil rows. COLA and COLb are first two columns in the primary key on the table. Here is my explain plan

|   0 | UPDATE STATEMENT              |                             |  5934K|   786M|   563M (20)|999:59:59 |        |      |            |
|   1 |  UPDATE                       | TABLE|       |       |            |          |        |      |            |
|   2 |   PX COORDINATOR              |                             |       |       |            |          |        |      |            |
|   3 |    PX SEND QC (RANDOM)        | :TQ10000                    |  5934K|   786M| 45978   (1)| 00:09:12 |  Q1,00 | P->S | QC (RAND)  |
|   4 |     PX BLOCK ITERATOR         |                             |  5934K|   786M| 45978   (1)| 00:09:12 |  Q1,00 | PCWC |            |
|*  5 |      TABLE ACCESS STORAGE FULL| TABLE|  5934K|   786M| 45978   (1)| 00:09:12 |  Q1,00 | PCWP |            |
|   6 |   TABLE ACCESS BY INDEX ROWID | TABLE    |     1 |   139 |     4   (0)| 00:00:01 |        |      |            |