High cardinality columns in indexes in DB2 require special ________ considerations.
- Index creation
- Maintenance
- Query planning
- Storage
High cardinality columns in indexes in DB2 require special storage considerations. High cardinality columns contain many unique values, which may lead to increased storage requirements and indexing overhead.
How are cardinality and ordinality represented in an ERD?
- By altering entity shapes
- Through color-coding
- Using text labels
- Via symbols and notation
Cardinality and ordinality in an Entity-Relationship Diagram (ERD) are typically represented through symbols and notation. These symbols, such as crow's feet and lines, indicate the cardinality (i.e., the maximum and minimum number of instances of one entity that can be associated with another) and ordinality (i.e., the sequence or order of occurrences) between entities. By understanding these representations, database designers and developers can accurately depict the relationships between entities in the database schema.
What is the primary purpose of creating views in DB2?
- Define security constraints
- Optimize query performance
- Provide data redundancy
- Simplify complex queries
Views in DB2 are primarily used to simplify complex queries by presenting a subset of data from one or more tables. They can hide the complexity of underlying table structures and provide a simplified interface for users to access data.
How does DB2 handle data integrity issues caused by concurrent transactions?
- DB2 automatically aborts one of the conflicting transactions to resolve data integrity issues.
- DB2 creates duplicate copies of conflicting data to prevent data integrity violations.
- DB2 ignores data integrity issues caused by concurrent transactions and allows inconsistent results.
- DB2 resolves data integrity issues by using locks to control access to shared resources during concurrent transactions.
DB2 employs various concurrency control mechanisms, such as locking and isolation levels, to manage data integrity issues arising from concurrent transactions. By using locks, DB2 ensures that only one transaction can access a specific resource at a time, preventing conflicting updates and maintaining data consistency. Additionally, DB2 supports different isolation levels, allowing users to control the visibility of changes made by concurrent transactions to address consistency requirements.
How does DB2 ensure data integrity within databases?
- ACID properties, BASE properties, CAP theorem, No data integrity mechanisms
- Data redundancy, Data inconsistency, Data fragmentation
- Referential integrity, Constraints, Data validation rules
- Transactions, No support for transactions, Data replication
DB2 ensures data integrity through various mechanisms such as referential integrity, constraints, and data validation rules. Referential integrity constraints enforce relationships between tables to maintain data consistency, while constraints and validation rules define permissible data values and ensure data accuracy. By adhering to these principles, DB2 maintains the integrity and reliability of the stored data.
Data compression in DB2 reduces the size of data by eliminating ________.
- Duplicate records
- Redundant information
- Unused space
- Unwanted data
Data compression in DB2 works by identifying and removing redundant information within the dataset. This can include eliminating duplicate records, reducing unused space, or removing any unnecessary data that might be present, ultimately leading to a reduction in the overall size of the data stored in the database.
What are the advantages of using a scrollable cursor in DB2?
- Allows for executing complex SQL queries
- Allows for fetching rows in both forward and backward directions
- Improves database security
- Provides a way to create temporary tables
Scrollable cursors in DB2 offer the advantage of fetching rows in both forward and backward directions. This is useful when navigating through large result sets, as it enables efficient data retrieval and manipulation. By using a scrollable cursor, developers can easily move back and forth within the result set without re-executing the query. This feature enhances application performance and user experience, especially in scenarios where users need to browse through extensive data sets.
Scenario: During peak hours, several users report slow query performance. How can the DB2 administrator identify the cause and resolve the issue promptly?
- Disable unnecessary applications to reduce system load
- Enable monitoring tools to capture SQL performance metrics
- Increase hardware resources such as CPU and memory
- Restart the DB2 instance to clear any temporary bottlenecks
Enabling monitoring tools to capture SQL performance metrics allows the DB2 administrator to identify poorly performing queries during peak hours. These tools can provide insights into various metrics such as execution time, I/O operations, and locking behavior, enabling the administrator to pinpoint the cause of slow query performance. Increasing hardware resources or restarting the DB2 instance may provide temporary relief but may not address the root cause of the issue. Disabling unnecessary applications can reduce system load but may not directly address SQL performance concerns.
Common troubleshooting methods for DB2 installation errors involve checking ________.
- Hardware compatibility
- Log files
- Network connectivity
- System requirements
Troubleshooting DB2 installation errors often involves examining log files generated during the installation process. Log files contain valuable information about errors, warnings, and other diagnostic messages, aiding in identifying and resolving installation issues.
In DB2, what type of data can be stored in XML or JSON format?
- Any structured data
- Binary data
- Numerical data
- Only textual data
In DB2, XML or JSON format can store any structured data, including textual, numerical, or binary data. This flexibility allows for versatile data storage and retrieval.