Major Description
As a follow up of OAK-5601: that one is about a situation where backgroundRead falls way behind and journal GC cleans up journal entries before it was able to read it. We should generally look into improving this situation, eg by having journal GC not do the clean up as long as there are instances that haven't read the entry. This could perhaps be achieved by periodically having each instance inform the rest about what journal entries it has processed (or simpler: how far back it would be find fine for journal entries to be GC'ed)
