Enable constraints/indexes in parallel?

I have been asked to look at setting up some scripts to re-enable constraints and indexes after they have been disabled by SQL*Loader. We want to do this because enabling these objects in with parallel clause is reported to be much faster than letting SQL*Loader enable them for us.
No matter what options I use in the the alter table command or the create index command, I can see no performance improvement at all. My overworked DBA says that there is probably an initialization parameter(s) that needs to be set at DB startup, but he is not aware of it and is too busy to look into it.
So my question is:
We are running Oracle 7.3.4 with parallel query option, what initialization parameters should be set to enable parallel index creation and contraint enabling?

Regards

            Mark Brayshaw - harried would-b assitant DBA Received on Thu Nov 12 1998 - 22:52:32 CST