Currently, there is no official documentation for database migration.

There is only this KB article which is inadequeate:

http://confluence.atlassian.com/display/CROWDKB/How+to+switch+Crowd+from+HSQL+to+an+external+database

We need better documentation, something like what Bamboo has:

http://confluence.atlassian.com/display/BAMBOO/Moving+your+Bamboo+Data+to+a+different+Database

We tell people that they should switch databases, without instructions on how to do so!