I noticed that session serialization currently does not work when there are pending inserts or deletes in the session (but AFAIK updates are not a problem). I'd really like to have this feature working even when the session contains dirty data. Can someone give me a hint as to why this limitation exists? And how hard would it be to implement?

ScheduledActions need to be made serializable for this, they aren't now. You would need to look at Hibernate 2.1 source and port the modifications over. There shouldn't be any complications with this, nobody did it yet because nobody needed it.

Thanks for confirming what I thought. I think I'll implement it and post the code in Jira.