Originally posted by hurleyb
Is this plausible and, if so, what is the mechanism?
Sure this is plausible, in fact it is a very common aproach with very large databases.

The mechanism? Well, you can't make a table or a partition a "read only" there is no such option. However you can make a tablespace read only. So the tables/partition that are not subject to changes should be moved to such read-only tablespaces. If you are putting partitions on read-only tablespaces, do not forget to do the same thing with their corresponding local indexes!

Once those segments are put on the read-only tablespaces you have to back those tablespaces only once as nothing ever change in them. Of course this is just in theory - in praxis you would still backup those tablespaces periodicaly, but much much less often than you back up your other read-write tablespaces.