Two-Phase-Locking

Question

Sort these various versions of Two Phase locking protocols in increasing order of restricted-ness:

1. 2-PL(normal)

2. S-2PL(Strict)

3. R-2PL(Rigorous)

4. C-2PL (Conservative)

5. LC-2PL(Lock Conversion)

Answer 1

Normal < Conservative < Strict < Rigorous.

1) In Rigorous 2PL, a transaction does not release any of it's locks until after it commits.

2) In Strict 2PL, a transaction does not release any of it's exclusive lock until after it commits.

This makes R-2PL more strict than S-2PL.

3) Conservative 2PL has no such lock release restrictions.

4) And Normal 2PL is the simplest one.

Comments

What about lock-conversion 2PL,i.e upgrading(shared to exclusive) and downgrading(exclusive to shared) of locks?

---

Tuhin Dutta 2-PL(normal) < lock-conversion 2PL