Describe the algorithm to draw the dependency graph, Database Management System

Describe the algorithm to draw the dependency graph?  

Ans: Algorithm to draw Precedence Graph is like this:

a.  For every transaction Ti participating in schedule S, make a node labeled Ti in the precedence graph.

b.  For every case in S where Tj executes a read_item(X) after Ti executes a write_item(X), create an edge (Ti→Tj) in the precedence graph.

c.  For every case in S where Tj executes a write_item(X) after Ti executes a read_item(X), create an edge (Ti→Tj) in the precedence graph.

d.  For every case in S where Tj executes a write_item(X) after Ti executes a write_item(X), create an edge (Ti→Tj) in the precedence graph.

e.  The schedule S is serializable if and only if the precedence graph has no cycles.

Posted Date: 5/4/2013 2:09:51 AM | Location : United States







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