"Suspending" indexes and constraint updates

Hi all.

I'd need to do large updates into already populated tables as
a maintenance activity.
The updates are generated by software and are consistent with
the constraints defined in the tables.

As of now I've been looking at the index and constraint definitions,
dropping them, doing the inserts and then re-creating both indexes and
constraints.
Is there a way to "suspend" the index updates and the constraint checks
before the inserts in order to later re-enable them and do a reindex?

TIA.

--
Reg me, please!