Transactions: Various Definitions Unclear from the Slides

[Kamiyu]

Hello,

These questions relate to Practice 4, and more generally to the scope of the exam/course.

Q6 mentions "basic 2PL", and Q7 mentions "strict 2PL", but when are these terms defined in the slides? From what I can see, no distinction between the two types is made (the word "basic" doesn't even appear in the slides), and there's only one mention of strict 2PL in the second set of slides, but this still doesn't explain what it is. Are we expected to know something not in the slides for the exam?

These terms are defined in the textbook, but there's also another two types alongside them, namely "conservative 2PL" and "Rigorous 2PL". Am I supposed to know these too?

In addition, Q7 also asks for a schedule that results in "write-read conflict", "write-write conflict", or "read-write conflict", but these terms are also not defined in the slides. The professor did verbally mention these terms during the lecture, but he gave a similar definition to the textbook, which is:

Two operations in a schedule are said to conflict if they satisfy all three of the following conditions: (1) they belong to different transactions; (2) they access the same item X; and (3) at least one of the operations is a write_item(X).  

By my understanding, this is just a way to classify the relationship between two operations within a transaction, i.e. they are either conflicting or not conflicting. So I don't understand part 1 to 3 in Q7, which asks us to create a schedule that results in a write-read/read-write/write-write conflict. Conflicts are a classification of all pair-wise relationships of operations in a schedule; this doesn't change no matter the schedule.

From googling it's clear that when used in this context, these terms have a different meaning to the above. But this is again something that is not mentioned anywhere in the slides.

Can you please clarify what exactly is expected knowledge? I've been going off "whatever is mentioned in the lecture notes", but the above shows that that isn't the case.

Thank you.

[Yu Hao]

For others who didn't join Prof. Lin's consultation:

Your solutions for the final exam should be based on Prof. Lin's lectures and lecture slides firstly, especially when there are conflicts between the lecture slides and textbook.