[ADMIN] Ideal way to upgrade to postgres 8.3 with less downtime

Hi, I have a database of size approx 400G. It's a 24/7 database. Only few tables have regular reads and writes. The other tables just store information. I would like to upgrade to 8.3 and would like to know the best way to upgrade with less downtime. Thanks Swathi

[ADMIN] User login

Hi, How do we find which user logged in from the OS level in postgres. For eg: If user "a" logged in from the OS level and logged into postgres psql as user "b" .how do we find the login details?