Virtual Gate Test Series: Databases - Schedules

Question

A' is set of all possible schedules

'C' is set of all possible schedules that are guaranteed to produce a correct final result

'S' is the set of all serializable schedules

'P' is the set of all schedules possible under 2-phase locking protocol 
Which is FALSE?

• A. $P\subseteq C$
• B. $S\subset P$
• C. $S\subseteq P$
• D. $P\subset C$

Comments

According to forouzan
"Although the 2PL guarantees serializability (that is, every schedule permitted is serializable, it doesnot permit all possible serializable schedule.(some serializable schedule prohibited by this protocol))"

What they mean by it?

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$T_{1}$	$T_{2}$
S(Y) R(X) U(Y)   E(X) R(X) X=X+Y W(X) UX(X)	S(X) R(X) U(X) E(Y) R(Y) Y=X+Y W(Y) UX(Y)

 

This is not 2PL, right?? because non-serializable. Then what locking is it?

P.S.-This diagram from forouzan

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Another question coming -

Why every 2PL need to be serializable? What is it's advantage??