After Metalink’s 10g and 11g Upgrade Companions now we also have a dedicated OTN database upgrade forum :)
Forum: Database – Upgrade
- Discuss all aspects of database upgrade from planning and testing through execution and troubleshooting. Also, information about helpful tools and utilities, documentation, and other information to make your database upgrade easier, faster, and less risky. -
Note:601807.1
11g Upgrade Companion
Note:466181.1
10g Upgrade Companion
Some Best Practices of Upgrading Oracle Database
http://tonguc.wordpress.com/2007/08/31/some-best-practices-of-upgrading-oracle-database/
