DBMS Concepts: Transactions, Data Integrity & NoSQL

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Questions and Answers

How does a DBMS ensure data integrity during concurrent transactions, and why is this important?

DBMS uses concurrency control mechanisms and ACID properties (Atomicity, Consistency, Isolation, Durability) to ensure data integrity. This prevents data corruption and ensures that each transaction is reliable and consistent.

Explain how the concept of data abstraction simplifies database interactions for different users.

Data abstraction hides the complexity of data storage from users through physical, logical, and view levels. This allows users to interact with the database without needing to know the underlying physical storage details, simplifying data access and management.

What is the significance of metadata in a DBMS, and how does it contribute to the self-describing nature of databases?

Metadata describes the structure, types, and constraints of the data within the database. It enables the database to be self-describing because it contains all the necessary information to understand the data without needing external documentation.

Compare and contrast logical and physical data independence in DBMS. Why are both important?

Logical data independence allows changes to the logical schema (e.g., adding a column) without affecting application programs. Physical data independence allows changes to the physical storage (e.g., changing hard drives) without affecting the logical schema. Both are important because they provide flexibility and maintainability, allowing changes without disrupting applications. Signup and view all the answers

Describe a scenario where using a NoSQL database would be more appropriate than using a relational database.

NoSQL databases are more appropriate when dealing with unstructured or semi-structured data, such as social media feeds or sensor data. They also excel in scenarios requiring high scalability and availability, where the strict schema requirements of relational databases would be too restrictive. Signup and view all the answers

In the context of database systems, what are the ACID properties, and why is each property crucial for ensuring reliable data management?

ACID stands for Atomicity, Consistency, Isolation, and Durability. Atomicity ensures that transactions are either fully completed or not at all. Consistency ensures that a transaction takes the database from one valid state to another. Isolation ensures that concurrent transactions do not interfere with each other. Durability ensures that once a transaction is committed, it remains so, even in the event of system failures. Each property is crucial for maintaining data integrity and reliability. Signup and view all the answers

Explain how concurrency control in a DBMS prevents issues like lost updates or dirty reads.

Concurrency control manages simultaneous access to the database by multiple users. It uses techniques like locking or multi-version concurrency control to prevent lost updates (where one transaction overwrites another's changes) and dirty reads (where a transaction reads uncommitted data), thus maintaining data integrity. Signup and view all the answers

Discuss the limitations of file-based systems that led to the development of DBMS. Provide specific examples of problems encountered in file-based systems.

File-based systems suffered from redundancy, where the same data was stored in multiple files, leading to inconsistency. They lacked data sharing and security, making it difficult for multiple users to access the same data securely. Data retrieval was also cumbersome due to the lack of structure, and there were difficulties with concurrency control and data integrity. Signup and view all the answers

How do the File Manager and Buffer Manager within the Storage Manager contribute to efficient data handling in a DBMS?

The File Manager organizes storage space on devices, while the Buffer Manager temporarily stores data in memory, reducing disk I/O and speeding up data access. Signup and view all the answers

Explain the roles of the DML Compiler and Query Optimizer in the Query Processor of a DBMS. How do they ensure efficient query execution?

The DML Compiler translates DML commands, and the Query Optimizer finds the most efficient execution plan. This minimizes resource usage and reduces query response time. Signup and view all the answers

In what ways do the Concurrency Control Manager and Recovery Manager work together within the Transaction Manager to maintain data consistency and integrity?

The Concurrency Control Manager prevents conflicts during simultaneous operations, while the Recovery Manager restores the database to a consistent state after failures. Signup and view all the answers

How does the Metadata Manager support other DBMS components in optimizing and executing queries?

The Metadata Manager provides other components with information about the database schema and structure, which is used for query optimization and efficient execution. Signup and view all the answers

Describe the role of the Database Engine in a DBMS, and explain how it interacts with stored data.

The Database Engine executes commands and interacts directly with the stored data, acting as the core component for data manipulation and retrieval. Signup and view all the answers

Explain how SQL and NoSQL databases differ in data structure, and provide examples of when each type would be most appropriate.

SQL databases use structured tables, while NoSQL databases use flexible formats. SQL is suitable for structured data, while NoSQL is better for unstructured or rapidly changing data. Signup and view all the answers

How does the structure of data within a relational database (SQL) differ from that in a non-relational database (NoSQL)?

Relational databases store structured data in tables with rows and columns, while non-relational databases use flexible formats like documents, key-value pairs, or graphs. Signup and view all the answers

Explain the role and importance of the Data Dictionary in a DBMS. How is this different from the metadata managed by the Metadata Manager?

The Data Dictionary stores metadata like table definitions and user privileges, while the Metadata Manager maintains and provides this information to other components. One is a repository, the other a service. Signup and view all the answers

How does a DBMS achieve data independence, and why is this beneficial?

DBMS achieves data independence by providing abstraction layers, ensuring changes at one level (e.g., physical storage) don't affect other levels (e.g., logical view). This reduces application maintenance and allows flexibility to change data storage. Signup and view all the answers

Explain the significance of ACID properties in transaction management within a DBMS.

ACID properties (Atomicity, Consistency, Isolation, Durability) ensure reliable transactions by guaranteeing that transactions are either fully completed or not at all (Atomicity), maintain data integrity (Consistency), operate independently (Isolation), and are permanently recorded once completed (Durability). Signup and view all the answers

Compare and contrast vertical and horizontal scalability in the context of database management systems.

Vertical scalability involves adding more resources to a single server, while horizontal scalability involves adding more servers to distribute the data. Vertical scaling has limitations, while horizontal scaling offers greater scalability and fault tolerance. Signup and view all the answers

In schema-less databases, how is data integrity typically ensured compared to databases with rigid schemas?

In schema-less databases, data integrity is often ensured through application-level validation, data governance policies, and techniques like schema-on-read. Rigid schema databases enforce integrity through predefined rules and constraints. Signup and view all the answers

Describe a scenario where a schema-less database would be more appropriate than a rigid schema database. Explain your reasoning.

Schema-less databases are appropriate for scenarios with rapidly changing data structures or when dealing with semi-structured/unstructured data, like social media feeds. This is because they offer flexibility and avoid the need for frequent schema changes. Signup and view all the answers

How does data abstraction simplify the interaction between users/applications and the database system?

Data abstraction hides the internal complexity of the database by providing different views of the data. This allows users/applications to interact with a simplified model without needing to understand the underlying storage and retrieval mechanisms. Signup and view all the answers

Explain how concurrency control works in a DBMS and why it is essential for multi-user environments.

Concurrency control allows multiple users to access the database simultaneously without conflicts. It's essential for multi-user environments because it ensures data integrity and prevents issues like lost updates or inconsistent reads through mechanisms like locking and versioning. Signup and view all the answers

Discuss the trade-offs between data redundancy control and data sharing in a DBMS, and how these objectives are balanced.

Data redundancy control aims to minimize duplicate data, while data sharing facilitates shared access to data. These objectives are balanced by using a centralized system that avoids unnecessary duplication while providing controlled access through views and permissions. Signup and view all the answers

Explain how a music streaming service could use a DBMS to reduce data redundancy and improve data consistency? Give a specific example.

A music streaming service can use a DBMS to store artist, album, and track information in a centralized database, eliminating duplicate entries across different playlists or user libraries. Ensuring that updates to artist information, such as a name change, are reflected consistently across the entire platform. Signup and view all the answers

Describe a scenario where the 'Backup and Recovery' merit of a DBMS would be critical for a streaming platform like Netflix? What specific type of failure could this protect against?

In the event of a server crash or a cyberattack that corrupts the database, the backup and recovery feature allows Netflix to restore the system to a previous state. This ensures minimal downtime and prevents loss of user data, streaming history, and licensing agreements. Signup and view all the answers

Explain a situation where the 'High Initial Cost' and 'Complexity' demerits of a DBMS might deter a small, independent film studio from using a DBMS for their video asset management.

A small film studio may find the initial investment in DBMS software, hardware, and training too expensive, especially if they have a limited budget. The complexity of setting up and maintaining the system, including database design and administration, may require specialized expertise that they lack, leading them to opt for simpler, file-based storage solutions. Signup and view all the answers

How could weak security in a DBMS lead to 'Potential Data Breaches' for a media company that stores sensitive information about its actors and contracts?

If a media company's DBMS has weak access controls or is vulnerable to SQL injection attacks, unauthorized individuals could gain access to sensitive actor information like contact details, financial records, or contract terms. A breach could lead to identity theft, financial loss, or reputational damage. Signup and view all the answers

Model a 'Movie' entity with at least three relevant attributes, one of which should be a composite attribute and specify which one it is.

Movie Entity: Attributes: Title, ReleaseDate (Composite Attribute: Month, Day, Year), Genre, and Director. Signup and view all the answers

In an Entity Relationship Diagram for a video streaming service, what type of relationship (unary, binary, or ternary) would best describe the interaction between users, movies, and reviews?

A ternary relationship would best describe the interaction because it involves three entities: Users (who write), Movies (that are being reviewed) and Reviews (the content provided). Signup and view all the answers

A 'Runtime' attribute of a 'Movie' entity is calculated from the 'EndTime' and 'StartTime' attributes. What type of attribute is 'Runtime', and how would it be represented in an Entity Relationship Diagram?

'Runtime' is a derived attribute, as it is calculated from other attributes. In an ERD, it is represented with a dashed oval. Signup and view all the answers

A 'Genre' attribute of a 'Movie' entity can have multiple values (e.g., Action, Comedy, Sci-Fi). What type of attribute is 'Genre', and how would it be represented in an Entity Relationship Diagram?

'Genre' is a multivalued attribute because a movie can belong to multiple genres. It is represented with a double oval in an ERD. Signup and view all the answers

Explain the difference between public, private, and protected visibility in UML class diagrams, providing a scenario for when each might be used.

Public members are accessible from anywhere, private members are only accessible within the class itself, and protected members are accessible within the class and its subclasses. Use public for providing an external interface, private for internal implementation details, and protected for allowing controlled access in inheritance. Signup and view all the answers

Describe the difference between an aggregation and composition relationship in UML, detailing how their lifecycles are dependent.

In aggregation, the related class can exist independently of the main class, whereas in composition, the related class's lifecycle is dependent on the main class. For example, a <code>Car</code> and <code>Engine</code> have a composition relationship because an <code>Engine</code> cannot exist without a <code>Car</code>. Signup and view all the answers

How does specialization in UML contribute to code reusability and maintainability? Give an example.

Specialization, or inheritance, allows new classes (subclasses) to inherit properties and methods from existing classes (superclasses), promoting code reuse and reducing redundancy. For example, <code>ElectricCar</code> and <code>GasCar</code> can inherit from a <code>Car</code> superclass, inheriting common attributes and methods. Signup and view all the answers

Illustrate a scenario where a Many-to-Many (M:N) relationship is appropriate in a database design, and describe how it is typically resolved.

A Many-to-Many relationship is appropriate when multiple instances of one entity can be related to multiple instances of another entity. This is generally resolved by introducing a junction table. For example, a <code>Student</code> can enroll in multiple <code>Courses</code>, and a <code>Course</code> can have multiple <code>Students</code>. The junction table (e.g., <code>Enrollments</code>) would contain foreign keys to both <code>Students</code> and <code>Courses</code>. Signup and view all the answers

Explain the role of interfaces in UML and how they enforce contracts between classes. Provide a simple example.

Interfaces define a contract that classes must adhere to by implementing all the methods declared in the interface. This ensures that different classes can be used interchangeably if they implement the same interface. Example: An interface <code>Taxable</code> might declare method <code>calculateTax()</code>, and different classes like <code>Product</code> and <code>Service</code> can implement this interface, providing their own tax calculation logic. Signup and view all the answers

Consider a system for managing library books and patrons. Describe the entities, relationships, and cardinalities you would use in an Entity-Relationship (ER) diagram.

Entities: <code>Book</code>, <code>Patron</code>. Relationship: <code>Borrows</code>. Cardinalities: One <code>Patron</code> can borrow many <code>Books</code> (1:N), and one <code>Book</code> can be borrowed by one <code>Patron</code> at a time (1:1) or many patrons over time(1:N). Signup and view all the answers

Explain why it is important to define multiplicity constraints in UML class diagrams?

Multiplicity constraints specify how many instances of one class can be associated with another, defining the boundaries of relationships. Defining multiplicity constraints helps in validating the data, enforcing business rules, and ensuring data integrity within an application's design. Signup and view all the answers

Given an online shopping system, describe the attributes you would expect to find for the 'Customer' class and provide visibility for each attribute? Briefly, explain why you chose the specified visibility.

Attributes could include: <code>customerID</code> (private - internal unique identifier), <code>name</code> (public - user-facing information), <code>email</code> (private - for secure communication), and <code>address</code> (protected - accessible to subclasses for shipping details). The <code>customerID</code> and email need to be kept secure so are private. <code>Name</code> needs to be public so it can be public facing. <code>address</code> is set to protected so additional classes can leverage it. Signup and view all the answers

Explain how the concept of specialization can be applied to a restaurant menu, providing specific examples of classes and subclasses.

A general class like <code>Entree</code> can be specialized into subclasses like <code>Vegetarian</code>, <code>GlutenFree</code>, and <code>Spicy</code>. Each subclass inherits properties from <code>Entree</code> (name, price) but has unique features such as ingredients or preparation methods. Signup and view all the answers

Describe how you might use interfaces to define the behavior of different types of cooking appliances in a restaurant kitchen.

An interface like <code>Cookable</code> could define methods such as <code>preHeat()</code>, <code>cook()</code>, and <code>clean()</code>. A microwave, oven, and grill would implement <code>Cookable</code>, each providing its way to execute these methods. Signup and view all the answers

How does the relationship between a Restaurant and a Food Item reflect a 1:M cardinality? Give an example.

One restaurant can offer multiple food items, but each food item belongs to only one restaurant. For example, <code>Pasta Carbonara</code> and <code>Caesar Salad</code> both belong to <code>Luigi's Italian Restaurant</code>, demonstrating many food items from one restaurant. Signup and view all the answers

Explain why concurrency control is important in a restaurant's online ordering system, and provide a specific scenario where it would be crucial.

Concurrency control prevents data inconsistency when multiple customers order simultaneously. For example, if two customers try to order the last plate of <code>Lobster Ravioli</code> at the same time, concurrency control ensures only one order goes through, preventing overselling. Signup and view all the answers

Describe the read, validation, and write phases in Optimistic Concurrency Control (OCC) and how they apply in a scenario where multiple users are updating inventory in a restaurant management system.

In OCC, each user reads inventory data, modifies it without locks, and then validates if any changes conflict with other updates before committing. If there's no conflict during validation, the changes are written; otherwise, the transaction is rolled back. If 2 managers try updating the quantity of <code>Chicken Tenders</code>, the second one to commit will have their changes rejected if the first one already committed. Signup and view all the answers

Explain how pessimistic concurrency control (PCC) can prevent conflicts in a restaurant table reservation system, and list one drawback of using PCC.

PCC prevents conflicts by locking a table when a reservation is being made. Other transactions must wait until the lock is released. A drawback is potential delays due to waiting for locks, affecting system responsiveness. Signup and view all the answers

Differentiate between a Shared Lock (S) and an Exclusive Lock (X) in the context of accessing a restaurant's database, and provide a use case for each.

Shared Lock allows multiple transactions to read the same data concurrently but prevents any transaction from writing. Exclusive Lock, on the other hand, allows only one transaction to read or write data, blocking all other transactions. A Shared lock is good for a manager running a sales report, and the Exclusive lock works for when a database admin wants to make schema changes. Signup and view all the answers

Consider a scenario where two chefs are trying to update the ingredients list for the 'Spicy Marinara Sauce' recipe stored in a database. One chef is adding `red pepper flakes`, and the other is increasing the amount of `basil`. Explain how a database system employing concurrency control would manage these updates to prevent data loss or corruption.

The database system uses locking mechanisms to manage concurrent updates. It acquires shared or exclusive locks on the shared data item (<code>Spicy Marinara Sauce</code> recipe). This ensures only one transaction can modify the recipe at a given time, preventing conflicts and ensuring the updates are applied in a consistent and isolated manner, maintaining data integrity. Signup and view all the answers

Flashcards

Rigid Schema

A predefined structure that must be followed in a database.

Schema-less

A flexible structure that allows dynamic changes in a database.