We have a product that uses SQL Server (currently 2019). We're moving to a different product, but will keep the database from the old product around for several years for reporting purposes.
Part of this project involves reviewing account permissions for who still needs access and revoking write permissions for most accounts that remain, since historical reporting data should not change. That is, we'll have very confidence data can no longer change at all in this DB.
As another part of this process, I am also considering changing the default isolation level for this database from the default READ COMMITTED to instead be READ UNCOMITTED. Since the data should no longer change, things like dirty reads, etc are no longer a concern, and in theory we can (at least marginally) improve performance by going to the less restrictive level.
The question is whether this is a good idea, and what drawbacks to this plan I might have missed.