We've done a backup and restore using native database backup tools as described in https://confluence.atlassian.com/display/JIRA050/Backing+Up+Data (we're on JIRA 5.0).
The restore seems to have been successful except that none of the user-installed plugins seem to have come across. I can't find any doco on why this might have happenened.
It might be worth noting that we forgot to back up the attachments from the data\attachments directory but I don't see how that could be related.
Also worth noting that this is a move from one server to another (from stage to prod).
Any ideas anyone?