Lesson 13

The key features of Oracle Shared Server that make it an invaluable tool for Oracle DBAs include:

1. Scalability: Oracle Shared Server can support a large number of concurrent users and sessions, making it ideal for high-volume applications.
2. Efficiency: Oracle Shared Server uses resources more efficiently than dedicated servers, requiring fewer processes and less memory. This can lead to significant performance improvements, especially on systems with limited resources.
3. Availability: Oracle Shared Server is more resilient to failures than dedicated servers. If a shared server process fails, the other shared server processes can continue to serve clients. This makes Oracle Shared Server a good choice for mission-critical applications.
4. Manageability: Oracle Shared Server is easier to manage than dedicated servers. This is because there are fewer processes to monitor and manage.

In addition to these key features, Oracle Shared Server also offers a number of other benefits, such as:

1. Improved performance for certain database features: Some database features, such as parallel execution and RAC, can perform better when using Oracle Shared Server.
2. Reduced memory usage: Oracle Shared Server uses less memory than dedicated servers, because it shares a single PGA across all shared server processes.
3. Reduced CPU usage: Oracle Shared Server can reduce CPU usage by offloading some tasks to the dispatcher process.
4. Simplified configuration and management: Oracle Shared Server is easier to configure and manage than dedicated servers, because there are fewer processes to monitor and manage.

Overall, Oracle Shared Server is a powerful and versatile tool that can be used to improve the performance, scalability, availability, and manageability of Oracle databases. Here are some specific examples of how Oracle DBAs can use Oracle Shared Server to improve their database environments:

1. Scalability: To improve the scalability of a database, Oracle DBAs can configure Oracle Shared Server to support a larger number of concurrent users and sessions. This can be done by increasing the number of shared server processes or by using dedicated servers for certain tasks, such as batch jobs.
2. Efficiency: To improve the efficiency of a database, Oracle DBAs can tune the Oracle Shared Server configuration parameters. For example, they can adjust the number of shared server processes, the PGA size, and the dispatcher queue size.
3. Availability: To improve the availability of a database, Oracle DBAs can configure Oracle Shared Server to be more resilient to failures. For example, they can use the dispatcher failover feature and the shared server failover feature.
4. Manageability: To improve the manageability of a database, Oracle DBAs can use the Oracle Shared Server monitoring tools. For example, they can use the V$SESSION view to view information about shared server sessions and the V$SESS_TIME_MODEL view to view information about shared server timeouts.

Overall, Oracle Shared Server is a valuable tool for Oracle DBAs who want to improve the performance, scalability, availability, and manageability of their database environments.

This module demonstrated that the Shared Server can be used as a command-line utility to manage Oracle databases. In addition, Oracle Shared Server's functionality is being merged into SQL*Plus, and that SQL*Plus now supercedes Server Manager as the command-line interface to Oracle. Some of the simpler Shared Server commands have been experimented with, and by now you are comfortable with starting Shared Server and connecting to a database. You should also be comfortable entering and executing commands and know how to recover when you mistakenly enter an invalid command.

This module introduced you to the following terms:

1. GUI: Graphic User Interface
2. environment variable: An environment variable is a dynamic-named value that can affect the way running processes will behave on a computer.
3. internal
4. X-Windows: The X Window System (X11, or simply X) is a windowing system for bitmap displays, common on Unix-like operating systems.
5. data dictionary:The data dictionary is the foundation of the database, and it is where the RDBMS finds which tables are in a database, which columns are in the tables, which columns are primary or foreign keys, and what type of data to expect in those columns.
6. headers:
7. package:A stored sub-program that combines PL/SQL procedures and functions into a single unit.

Headers play a role in Oracle Shared Server. Headers are used to provide information about a request or response, or about the data contained in the message body. In Oracle Shared Server, headers are used to communicate between the client and the shared server process. Here are some of the ways that headers are used in Oracle Shared Server:

• To identify the type of request: The request header includes a field called `METHOD` that specifies the type of request, such as `GET`, `POST`, or `PUT`. This information is used by the shared server process to determine how to handle the request.
• To specify the request body: The request header includes a field called `CONTENT-LENGTH` that specifies the length of the request body. This information is used by the shared server process to read the request body from the client.
• To provide authentication credentials: The request header may include fields called `AUTHORIZATION` or `WWW-Authenticate` that provide authentication credentials. This information is used by the shared server process to verify the identity of the client.
• To indicate the desired response format: The request header may include a field called `Accept` that indicates the desired response format, such as `HTML` or `XML`. This information is used by the shared server process to format the response.

Headers can also be used to provide additional information about the request, such as the client's IP address, the user agent, and the referer. This information can be used by the shared server process to troubleshoot problems or to provide additional security measures.
In addition to being used to communicate between the client and the shared server process, headers can also be used to communicate between the shared server process and the Oracle database. For example, the shared server process can use headers to send information about the request to the database, such as the SQL statement to execute. The database can then use this information to process the request and return the results to the shared server process. Headers are an important part of Oracle Shared Server and play a vital role in communication between the client, the shared server process, and the Oracle database.