The ofMucConversationLog table is the persistence of MUC room messages that openfire uses to load MUC history from. This database table only stores the body portion of the groupchat stanza. Users may have extensions or xhtml included in the groupchat message, these portions are lost when the Openfire server is restarted.
Message ID, Thread ID and other properties aren't stored either.
This is problematic if you want to archive groupchat messages in a client database. Due to the lack of the ID you can't easily know if the groupchat message is already in your archive.
(because if you rejoin you receive the history messages again).