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Nilanjan Bhowmick AIR 3, CSIR NET (Earth Science)
- UGC NET
- Computer Science & Applications
May anyone explain me serializability?
May anyone explain me serializability? Especially precedence graph
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Aparna 1
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• Serializability is a concurrency scheme where the concurrent transaction is equivalent to one that executes the transactions serially. • In simple words, serializability checks that whether the non-serial schedule is equivalent to the serial schedule or not ? • It helps to identify which non-serial schedules are correct and will maintain the consistency of database. It preserve the consistency and concurrency of a database. • It ensures that a schedule for executing concurrent transactions is equivalent to one that executes the transactions serially in some order. • It helps to check which schedules are serializable ? • Serializability is used to keep the data in a consistent state. • Two types of serializability - 1. Conflict Serializability 2. View Serializability • The “serialization graph” or “precedence graph” is used to test the serializability of a schedule. It has a pair G = (V, E), where E consists of a set of edges, and V consists of a set of vertices. The set of vertices contain all the transactions participating in the S schedule. The set of edges contains all edges Ti Tj for which one of the following three conditions satisfy - 1. Create a node Ti ->Tj, if Ti transaction executes write (Q) before Tj transaction executes read (Q). 2. Create a node Ti ->Tj, if Ti transaction executes read (Q) before Tj transaction executes write (Q). 3. Create a node Ti ->Tj, if Ti transaction executes write (Q) before Tj transaction executes write (Q). • If a precedence graph for any schedule contains a cycle, then that schedule is non-serializable. If the precedence graph has no cycle, then the schedule is serializable.
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Aparna
Serializability checks that whether the non-serial schedule is equivalent to the serial schedule or not ? It helps to identify which non-serial schedules are correct and will maintain the consistency of database. It preserves the consistency and concurrency of a database. It helps to check which schedules are serializable ? Serializability is used to keep the data in a consistent state. Two types of serializabilty- 1. Conflict Serializability and 2. View Serializability . The "serialization graph" or "precedence graph" is used to test the serializability of a schedule. If precedence graph for any schedule contains a cycle, then that schedule is non-serializable.If the precedence graph has no cycle, then the schedule is serializable.
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Aparna
Serializability is a concurrency scheme where the concurrent transaction is equivalent to one that executes the transactions serially.
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Reenu
Serializability is the classical concurrency scheme. It ensures that a schedule for executing concurrent transactions is equivalent to one that executes the transactions serially in some order. It assumes that all accesses to the database are done using read and write operations