The data dictionary and dynamic performance views are two essential components of a relational database management system (RDBMS) that provide information about the database and its performance.
Data Dictionary
The data dictionary is a collection of read-only tables and views that contain metadata about the database.
This metadata includes information about the following:
- Schema objects: tables, views, indexes, stored procedures, etc.
- Data types: definitions and attributes of data types used in the database.
- Users and privileges: user accounts and access permissions for different objects.
- Constraints: rules that enforce data integrity and consistency.
- Storage information: location and allocation of data files.
The data dictionary is used for various purposes, such as:
- Understanding the structure of the database: users can query the data dictionary to find information about the schema objects, data types, and constraints.
- Monitoring system health: administrators can monitor the data dictionary to identify potential issues and problems.
- Developing applications: developers can use the data dictionary to understand the structure of the database and write queries to access and manipulate the data.
Dynamic Performance Views
Dynamic performance views are specialized read-only views that are continuously updated to reflect the current performance of the database.
These views provide information about various aspects of database performance, such as:
- Session activity: user sessions, locks, and blocking.
- SQL statement execution: statistics on how long queries are taking to execute.
- Resource utilization: CPU, memory, and disk I/O usage.
- Wait events: the reasons why sessions are waiting for resources.
Dynamic performance views are used for various purposes, such as:
- Identifying performance bottlenecks: administrators can analyze the performance views to identify areas where the database is slow or inefficient.
- Tuning SQL statements: developers can analyze the performance views to optimize the execution of their queries.
- Troubleshooting problems: administrators can use the performance views to diagnose and resolve performance problems.
Relationship between Data Dictionary and Dynamic Performance Views
- The data dictionary and dynamic performance views are complementary tools that provide valuable information about the database.
- The data dictionary provides a static view of the database structure, while the dynamic performance views provide a real-time view of the database performance.
- By using these two tools together, administrators and developers can gain a comprehensive understanding of the database and ensure that it is performing optimally.
Differences between the data dictionary and dynamic performance views
| Feature | Data Dictionary | Dynamic Performance Views |
| Purpose | Provide metadata about the database | Provide information about the database performance |
| Content | Schema objects, data types, users, constraints, etc. | Session activity, SQL execution statistics, resource utilization, wait events, etc. |
| Update frequency | Read-only | Continuously updated |
| Use cases | Understanding the database structure, monitoring system health, developing applications | Identifying performance bottlenecks, tuning SQL statements, troubleshooting problems |