Prelim 1 Grading Guide

Problem 1: 2PC (20 pts)

1.a: 4 pts
Maximum is missing: -1

1.b: 4 points
Referring only to the expected values of the variables: -2
Referring to reasons different than parallel txns and expected values: -3

1.c: 4 points

1.d: 4 points

1.e: 4 points
Referring only to the transaction time: -2
Referring to reasons different than in-doubt txns and txn time : -3

Problem 2: SAGAs (15 pts)

Reordering txns: 10 points
Introduce txn boundaries where it makes sense: 5 points

Problem 3: Partitioning vs. Replication (25 pts)

3.a: 10 points
A good answer for each scheme: 5 points
No discussion about scalability: -1
No discussion about key distributions: -1
Wrong terms in each formula -5
A wrong term in a formula -2
Wrong scalability reason -1

3.b: 10 points
A good answer for each scheme: 5 points
Wrong terms in each formula -5
A wrong term in a formula -2

3.c: 5 points
Replicating only a part of the set -2

Problem 4: Recovery Using Device State and Idempotency (20 pts)

No discussion about the device behavior at errors -1
No discussion about the device's good behavior -1
No log discussion -3
No description of logged steps -3
No transaction split in steps -3
A wrong transaction split -1

Problem 5: Session State (20 pts)

Good discussion of the problem: 7 points.
A working but not especially efficient solution: 8 points.
Aborting a request that arrives before the previous responnse has been sent (incorrect semantics - they should be serialized): -2
I did not take off points for not considering the "mega-proxy" problem (requests from the same client/session need not come from the same IP when there are multiple load-balanced proxies).
Particularly clever or efficient solution: up to 5 additional points.