How to speed up an update

I am trying to tune the following update:

update TABLE set column = decode (column, vlaue1..);

The TABLE has about 13mil rows and a primary key. I am thinking of dropping the PK and running the update
with higher degree of parallelism and rebuilding the PK after the update. Is there anything else I should consider? I am running oracle 10.2.0.2

thank you

Gene Gurevich

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