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Transactions And Concurrency Management
Introduction
One of the main benefits of storing data in an integrated repository or a database is to permit sharing of it between multiple users. Various users access the database or perform transactions at the similar time. What if a user's transactions try to access a data item that is being used /modified by another transaction? This unit attempts to give details on how concurrent transactions are implemented under the control of DBMS. Though, in order to describe the concurrent transactions, first we must explain the term transaction.
Concurrent implementation of user programs is essential for good performance of DBMS, as concurrent running of various user programs keeps utilizing CPU time efficiently, as disk accesses are frequent and are relatively slow in case of DBMS. Also, a user's program may carry out a lot of operations on the data returned from DB, but DBMS is only concerned about what data is being written from / read / into the database.
If R1 and R2 are two relations or functions, then the result of R3 = R1 × R2 is the combination of tuples that are in R1 and R2. The product is associative and commutative. Degr
We are looking to find someone to prepare a database which improves upon the one we are using at present. The present database will be found here: Click on filter options and yo
Define lock? Lock is the most common used to execute the requirement is to permit a transaction to access a data item only if it is currently holding a lock on that item.
What is relational model feature? A relational model feature is much more data independence than some other database models.
What are the Objectives of object design After going through this unit, you could be able to: explain steps of object design; discuss algorithms that reduce costs;
Rules Of Data Normalisation Let us now summarise Normalisation with the help of various clean rules. The following are the necessary rules for the Normalisation process: 1.
What are called journaling file systems? File systems that support log disks are known as journaling file systems.
You have a friend that runs a motor bike club that holds racing events at various venues on weekends, on a monthly basis. Some venues are private race tracks and some are dirt trac
how to write a in a text and load it on mysql
Using Column aliases Example: To print column names as NAME and ANNUAL SALARY SELECT ENAME "NAME", SAL*12 "ANNUAL SALARY" FROM EMP;
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