Tom Kyte recorded a podcast this month about the new features of Oracle Database 11gR2. The podcast, part of the Oracle Database podcasts series, can be accessed here:
In it, he describes an exciting new feature: the ability to compile stored procedures, packages, etc. while users are online using the same schema! The feature, called Edition-based Redefinition, refers to the current objects as an "edition". The developer creates a child edition based upon the current one, then does development against the child edition. When it comes time to switch over, new sessions can begin using the new edition, as existing sessions continue to use the old. An upgrade that used to take an hour of downtime for compilations can appear to users to take no time at all. It still takes an hour to compile, he said, but the users are not locked out of the system while it's happening.
He also talks about the ability to create a table, but defer to allocation of storage until the table is first used. This will make it much faster to install complex software applications that have many optional tables in them. Only the metadata in the data dictionary will be created during the install, and tables never used will therfore not take up space.
It's a short talk, about 10 minutes, but well worth listening to.