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Suppose a database schedule S involves transactions T1, …,Tn. Construct the precedence graph of S with vertices representing the transactions and edges representing the conflicts. If S is serializable, which one of the following orderings of the vertices of the precedence graph is guaranteed to yield a serial schedule? 

Suppose a database schedule S involves transactions T1, …,Tn. Construct the precedence graph of S with vertices representing the transactions and edges representing the conflicts. If S is serializable, which one of the following orderings of the vertices of the precedence graph is guaranteed to yield a serial schedule?  Correct Answer Topological order

Serial schedule is possible only when precedence graph doesn’t contain cycle. If precedence graph contains a cycle, it means schedule is not conflict serializable.

Breadth first search and Depth first search of a graph are possible even if graph contains cycle.

Topological sort in a graph will not work if graph contains a cycle.

Consider a directed acyclic graph:

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Here Two orders possible: V2, V3, V1, V4, V5, V6 OR V3, V2, V1, V4, V5, V6.

In case of ascending order of transaction indices, two non-conflicting schedules can occur simultaneously.

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