what to do with hanging database

Here's the citation from article 'Oracle Database 10g: Top Features for DBAs: Part 3—Performance Features' by Arup Nanda:

Let's assume that you use Oracle Enterprise Manager to diagnose and solve performance issues. One day, a nasty issue arises: a badly designed application is causing serious library-cache lock issues and the database appears to be hung. You have to quickly identify the culprit sessions and kill them quickly.

You could bring up Oracle Enterprise Manager to diagnose this issue. But, wait! If the entire database is saturated with hung sessions, wouldn't the query from Oracle Enterprise Manager hang as well?

With Oracle Database 10g Release 2, the answer is "no."

Actually, the answer is "no" for 8i, 9i and 10g r1 also!

I mean that even we can't use Enterprise Manager still we can use hanganalyze event (starting from 8.1.6) as quick (real quick on hanging databases) and easy way to solve 'hanging database' issue.

And remember, that we can use hanganalyze event even if we can't connect to database at all -- I explained how to do it in my previous post.