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Lock Based Protocol
A lock is nothing but a mechanism that tells the DBMS whether a particular data item is being used by any transaction for read/write purpose. As there are two types of operations, i.e. read and write, whose basic nature are dissimilar, the locks for read and write operation might be behave differently.
Read operation performed by dissimilar transactions on the same data item poses less of a challenge. The value of the data item, if constant, can be read by any number of transactions at any given time.
Components of database manager The above functions are reached by the database manager. The major elements of a database manager are: Authorisation control: This mod
Explain the term- signal-to-noise ratio A signal-to-noise ratio of 20 dB means that S/N = 100. As log2101 is around 6.658, the Shannon limit is around 19.975 kbps. The Nyquist
CREATE TABLE prodtrans ( pno number (4) ptype char (1) CHECK (ptype in ('I','R','S')), qty number (5) FOREIGN KEY pno REFERENCES product (pno) ON DELETE CASCADE);
Isolation or Independence : The isolation property shows that the updates of a transaction should not be visible till they are committed. Isolation assurance that the progresses of
Example - ALTER TABLE emp MODIFY (empno NUMBER (7));
explain cascading rollback
A relation has: Relational Schema Relation instance Relational Schema: A relational schema shows the relation's name, its attributes and the domain of every a
What is DML (Data Manipulation Language)? This language that enable user to access or manipulate data as organised by appropriate data model. Procedural DML or Low level: DM
Can you help me with the following: Drop statements for all objects in the lab project. Create statements for all objects of the lab project Create indexes for foreign keys Cre
Which are the two ways in which entities can participate in a relationship? Total and partial are the two ways in which entities can participate in a relationship
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