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Database training
4.2.04. 2PL: Guaranteed serializable
T
1
read_lock(Y);
read_item(Y);
write_lock(X);
unlock(Y);
read_item(X);
X=X+Y;
write_item(X);
unlock(X);
T
2
read_lock(X);
read_item(X);
write_lock(Y);
unlock(X);
read_item(Y);
Y=X+Y;
write_item(Y);
unlock(Y);
Less efficient (cost), but serializable
‹ 4.2.03. A typical transaction pair
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4.2.05. Guarantee cost ›
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