Email due at midnight on Monday, December 2, 2019. (Strongly prefer plain text. Will accept PDF or MSWord documents, if typed.) Email subject should be "cs4250,hwk4".
Handwritten answers, on paper or as photographs, will not be accepted.
This is an individual assignment. All work must be your own. You should not look at any other student's work (in whole or in part, on paper or on screen), nor allow anyone else to look at yours, during the course of this assignment.
Note: T<number> identifies a transaction numbered number. R(<letter>) identifies a read operation on database object letter. W(<letter>) identifies a write operation on database object letter.
T1: R(A), T1: R(B), T2: R(B), T2: W(B), T3: R(A), T3: W(A), T2: R(A), T2: W(A), T1: R(D), T1: W(D), T3: W(C), T3: R(B)
Is the schedule serializable? If so, show an equivalent serial transaction order. If not, precisely describe why not.
If relevant, fill in this table with the equivalent serial transaction
order. Time proceeds from left to right, with only one action possible in each
time slot.
| Serializable Schedule | Time 1 | Time 2 | Time 3 | Time 4 | Time 5 | Time 6 | Time 7 | Time 8 | Time 9 | Time 10 | Time 11 | Time 12 | Time 13 | Time 14 | Time 15 |
| T1 | |||||||||||||||
| T2 | |||||||||||||||
| T3 |
T2: W(A), T3: R(A), T1: R(A), T3: R(A), T2: R(B), T2: W(B), T1: W(A), T3: R(B), T3: W(B), T1: R(C), T2: R(C)
Is the schedule serializable? If so, show an equivalent serial transaction order. If not, precisely describe why not.
If relevant, fill in this table with the equivalent serial transaction
order. Time proceeds from left to right, with only one action possible in each
time slot.
| Serializable Schedule | Time 1 | Time 2 | Time 3 | Time 4 | Time 5 | Time 6 | Time 7 | Time 8 | Time 9 | Time 10 | Time 11 | Time 12 | Time 13 | Time 14 | Time 15 |
| T1 | |||||||||||||||
| T2 | |||||||||||||||
| T3 |
For questions 3-5, consider the execution of the ARIES recovery algorithm given the following log:
| LSN | Log Record |
| 00 | begin_checkpoint |
| 05 | end_checkpoint |
| 10 | Update: T3 writes P1 |
| 20 | Update: T1 writes P1 |
| 30 | Update: T1 writes P3 |
| 40 | T3 commit |
| 50 | Update: T2 writes P2 |
| 60 | T1 abort |
| 70 | CLR: Undo T1 LSN 30 |
| 80 | Update: T4 writes P2 |
| 90 | T3 end |
| 100 | T2 abort |
| 110 | Update: T4 writes P1 |
| X - crash, restart |
For the questions below, when you are asked which log records are read, you are to supply the exact list of LSNs from log above. When data pages are asked for, you are to supply the exact list of page identifiers from the log above. And so on. Be specific and concrete in your answers, answering specifically for the provided log.
Operations can be identified using the LSN for the log record recording that operation. (So, of course, can the log record itself.)
Generic statements or quotations from the textbook will earn 0 points. Example: "all the pages" == 0 points. "P1, P2 and P3" == more than 0 points, assuming those are the pages read.
For questions 3-5, parts a-c are separate questions. Answer a through c separately. Label your answers so that it is clear what is your answer to '3.a' and what is your answer to '4.c', and so on.