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Tag Archives: DBMS-Transactions and Concurrency Control

Prerequisite: Conflict Serializability, Precedence Graph Conflict Serializable Schedule: A schedule is called conflict serializable if it can be transformed into a serial schedule by swapping… Read More
Concurrency control means that multiple transactions can be executed at the same time and then the interleaved logs occur. But there may be changes in… Read More
States through which a transaction goes during its lifetime. These are the states which tell about the current state of the Transaction and also tell… Read More
Time Stamping Protocols: The timestamp protocols ensures that each transaction in the system has in advance a timestamp that has been associated with each transaction… Read More
Algorithm for Recovery and Isolation Exploiting Semantics (ARIES) is based on the Write Ahead Log (WAL) protocol. Every update operation writes a log record which… Read More
Concurrency control is provided in a database to: (i) enforce isolation among transactions. (ii) preserve database consistency through consistency preserving execution of transactions. (iii) resolve… Read More
When multiple transactions execute concurrently in an uncontrolled or unrestricted manner, then it might lead to several problems. These problems are commonly referred to as… Read More
Generally, there are 3 types of schedule based on recoverbility given as follows: Recoverable schedule: Transactions must be committed in order. Dirty Read problem and… Read More
Prerequisite – Concurrency Control -Introduction, Conflict Serializability, Transaction Isolation Levels in DBMS Serializability: If any transaction (non-serial) produce a outcome which is equal to the… Read More
Basically, whenever a transaction is submitted to a DBMS for execution, the operating system is responsible for making sure or to be confirmed that all… Read More
Prerequisite – Timestamp Ordering Protocols In the various Concurrency Control schemes have used different methods and every individual Data item as the unit on which… Read More
Timestamp Ordering Protocol states that if Ri(X) and Wj(X) are conflicting operations then Ri (X) is processed before Wj(X) if and only if TS(Ti) <… Read More
We have discussed briefly about the first type of Concurrency Control Protocol, i.e., Lock based Protocol. Now, recalling where we last left off, there are… Read More
Prerequisite : Conflict Serializability Precedence Graph or Serialization Graph is used commonly to test Conflict Serializability of a schedule. It is a directed Graph (V,… Read More
  A transaction is a single logical unit of work which accesses and possibly modifies the contents of a database. Transactions access data using read… Read More