We use the RecoveryUnit snapshot ID for comparison purposes to tell us two things:

• Has my snapshot changed on the same RecoveryUnit? (e..g normal yielding)
• Has my snapshot changed from a different RecoveryUnit? (e.g. with getMore)

We need to maintain that snapshot IDs are globally unique, but instead of incrementing the atomic for every snapshot, we can just have a globally unique RecoveryUnit ID and a locally unique snapshot counter for each RecoveryUnit. This should be sufficient to reduce contention on the Snapshot ID atomic and still maintains uniqueness.