I turned off constraint checks for foreign keys in my central table – this worked wonders for me. But your mileage may vary depending on the amount of contention you face.
In this case, my table was frequently updated even though none of the updates modified the foreign keys. But y removing the foreign key constraint check (the check not the foreign key relation-ship), i was able to see significant improvements.
I do not have the exact figures but i belive it was to the tune of 40-50% or so.
Disclaimer – Of-course i hope you know what removing of the FK constraint check implies
Disclaimer – I turn off the checks only weeks before the final release, and make a range of unit tests apart from having a dedciated test team to run more tests. If you rely on the Fk constraint to catch errors this is not recommended