I have written and presented a Master Class on Database links this year to two UKOUG DBA SIGs and added it to my “Articles and Presentations” page. This forms part one of a two part series on DB Links which covers: the various DB Link Options, Remote Queries, Performance implications for DB Links, Security using DB Links and Implications for Administration. Part two will be presented at the UKOUG annual conference and will cover: remote and distributed queries, remote and distributed transactions; Oracle two-phase commit processing and recovery implications of distributed systems.
If you are interested in DB Links and Distributed Systems then have a look at Database Links Master Class Part 1.