4,039 views
7 votes
7 votes
Number of conflict serializable schedules in

T1 : R(A) W(A) R(B) W(B)

T2: R(A) W(A) R(B) W(B)

5 Answers

11 votes
11 votes

answer is 12

 

similary to for

case t2->t1 you will get 6 more

NOTE:

in 12 schedule 2 serial schdeule is also included

5 votes
5 votes
Schedules conflict equivalent to serial schedule $T1 \rightarrow T2 :$

$R2(A) $ must occur after $W1(A),$ and $R2(B)$ must occur after $W1(B)$ and within a transaction, order of operations must remain same, hence,  The only possibility is $R1(A), W1(A),\_,\_,\_,\_,R2(B), W2(B)$, in those four blank spaces, we  can put remaining operations, hence, $4!/(2! \times 2!)$

Similarly for Schedules conflict equivalent to serial schedule $T2 \rightarrow T1 .$

Hence, answer 12.
4 votes
4 votes
$\color{REd}{T_1\rightarrow T_2}$

$1) $   $R_1(A) \ W_1(A)\  R_1(B)\  W_1(B)\ $$\color{darkblue}{ \ R_2(A)\  W_2(A)\  R_2(B)\  W_2(B)}$

$2) $   $R_1(A) \ W_1(A)\  R_1(B)\ \color{darkblue}{R_2(A)} W_1(B)\ $$\color{darkblue}{ \ \  W_2(A)\  R_2(B)\  W_2(B)}$

$3) $   $R_1(A) \ W_1(A)\ \color{darkblue}{R_2(A)} \  R_1(B)\  W_1(B)\ $$\color{darkblue}{ \ \  W_2(A)\  R_2(B)\  W_2(B)}$

$4) $   $R_1(A) \ W_1(A)\ \color{darkblue}{R_2(A)\ } \  R_1(B) \ \ \color{darkblue}{W_2(A)} W_1(B)\ $$\color{darkblue}{ R_2(B)\  W_2(B)}$

$5) $   $R_1(A) \ W_1(A)\ \color{darkblue}{R_2(A)\ W_2(A)} \  R_1(B) \ \  W_1(B)\ $$\color{darkblue}{  R_2(B)\  W_2(B)}$

$6) $   $R_1(A) \ W_1(A)\  R_1(B)\  \ \color{darkblue}{R_2(A)\ W_2(A)} W_1(B)$$\color{darkblue}{ \  R_2(B)\  W_2(B)}$

$\color{REd}{T_2\rightarrow T_1}$

$6$ schedules : same as above just change of subscript.

Total : $6+6=12$ schedules
3 votes
3 votes





do same for T2----->T1 
and two more Serial Schedule T----->T2, T2----->T1

Two interleaving and two Serial Total four Conflict Serialisable Schedule Possible..

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