This bug has very simple workarounds. It will probably be fixed in the next major release.
Report by William Pietri:
> Suppose in version 1 of the software I have a bunch of transaction
> A. In version 2, this transaction is removed. It seems like even if
> I snapshot as the last thing before shutdown and upgrade, Prevayler
> will still read the last journal, even though it doesn't need to.
> Won't this result in a ClassNotFoundException as it tries to load
> and discard the copies of transaction A in the journal?
1) To keep the class of Transaction A around, even if it is no longer being used.
2) To delete or move the old journal files to another directory.