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oracle kill session by sql_id with code examples

Sricharan S

Oracle is an industry-leading database management system often used by businesses and organizations of all sizes. One important capability of Oracle is the ability to kill sessions based on their SQL ID. This functionality can be incredibly useful for system administrators and developers who need to quickly terminate long-running or problematic queries.

In this article, we will explore how to kill sessions by SQL ID in Oracle, including an overview of the relevant commands and code examples.

What is a SQL ID?

Before we begin discussing how to kill sessions by SQL ID, it is important to understand what a SQL ID is. In Oracle, a SQL ID is a unique identifier that is assigned to each SQL statement that is executed on the system. This identifier can be used to identify and locate specific queries within the database.

How to Find a SQL ID

To find a SQL ID for a particular query in Oracle, you will need to use the V$SQL view. This view contains information about all SQL statements that have been executed on the system, including their SQL ID.

To find the SQL ID for a specific query, you can run the following SQL statement:

SELECT sql_id FROM v$sql WHERE sql_text LIKE '%YOUR_QUERY_HERE%';

This will return the SQL ID for any statement containing the specified text. You can then use this SQL ID to kill the session that the statement is associated with.

How to Kill a Session by SQL ID

Once you have located the SQL ID for a problematic query, you can use the ALTER SYSTEM KILL SESSION command to terminate the associated session. This command can only be executed by a user with the appropriate privileges (such as a system administrator).

The syntax for the KILL SESSION command is as follows:

ALTER SYSTEM KILL SESSION '{SQL_ID}, {SESSION_SERIAL#}';

Here is an example of how to use this command to kill a session by SQL ID:

ALTER SYSTEM KILL SESSION '4rggk7bna8m3u, 12345';

This command will terminate the session associated with the SQL ID "4rggk7bna8m3u" and session serial number "12345".

It should be noted that using the KILL SESSION command can have unintended consequences if used improperly. Killing a session abruptly can cause data loss or corruption, so it should only be used as a last resort. It is recommended to first try to diagnose and resolve any underlying problems with the query before resorting to killing the associated session.

Code Example

Let's take a look at a full code example to see how killing a session by SQL ID works. In this example, we will assume that we have identified a problematic query that is causing performance issues and we need to terminate the associated session.

  1. First, we will locate the SQL ID for the problematic query using the following SQL statement:
SELECT sql_id FROM v$sql WHERE sql_text LIKE '%YOUR_QUERY_HERE%';

This will return the SQL ID for the statement that contains the text specified in the query.

  1. Next, we will use the ALTER SYSTEM KILL SESSION command to terminate the associated session:
ALTER SYSTEM KILL SESSION '{SQL_ID}, {SESSION_SERIAL#}';

For example, if the SQL ID was "4rggk7bna8m3u" and the session serial number was "12345", the command would look like this:

ALTER SYSTEM KILL SESSION '4rggk7bna8m3u, 12345';
  1. After executing the KILL SESSION command, we can verify that the session has been terminated using the following SQL statement:
SELECT * FROM v$session WHERE sid = {SESSION_ID};

Replace {SESSION_ID} with the identifier associated with the session you just killed. If the session has been terminated successfully, this query should return no rows.

Conclusion

Killing sessions by SQL ID can be a powerful tool for managing and troubleshooting performance issues in Oracle. By locating and terminating problematic queries, system administrators and developers can improve overall system performance and stability.

However, it is important to use caution when using the KILL SESSION command, as it can cause data loss or corruption if not used properly. It is recommended to only use this command as a last resort after attempting to diagnose and resolve any underlying problems with the query.

With the information and code examples provided in this article, you should now have a basic understanding of how to kill sessions by SQL ID in Oracle.

Sure! Let's dive deeper into some of the topics discussed in the previous article.

SQL IDs and how to find them

As we mentioned earlier, SQL IDs are unique identifiers assigned to each SQL statement that is executed within the system. These IDs can be used to locate the problematic queries that are causing issues within the database.

There are several ways to find SQL IDs in Oracle. One way to find them is by using the V$SQL and V$SQLAREA views. These views store information about all SQL statements executed on the system, including their SQL IDs.

Here's an example query to find SQL IDs using the V$SQL view:

SELECT sql_id, sql_text
FROM v$sql
WHERE sql_text LIKE '%YOUR_QUERY_HERE%';

By replacing "YOUR_QUERY_HERE" with the text you're looking for, this query will return all SQL IDs and their corresponding text that contain the specified text.

Another way to find SQL IDs is by using the SQL_ID() function. This function returns the SQL ID for the currently executing SQL statement. You can run the following query to find the SQL ID for a currently executing SQL statement:

SELECT SQL_ID
FROM V$SESSION
WHERE AUDSID = USERENV('SESSIONID');

Once you have the SQL ID for the problematic query, you can then use it to kill the associated session using the ALTER SYSTEM KILL SESSION command.

The ALTER SYSTEM KILL SESSION command

The ALTER SYSTEM KILL SESSION command is used to terminate a user session in Oracle. It can be used to terminate a session due to a long-running query, a user error, or other reasons.

Here's the basic syntax for the command:

ALTER SYSTEM KILL SESSION '{SQL_ID}, {SESSION_SERIAL#}';

To use this command, you need to replace {SQL_ID} with the SQL ID for the problematic query and {SESSION_SERIAL#} with the session's serial number. This will terminate the session associated with the query.

It's important to note that this command can cause unexpected issues, so it should only be used as a last resort. Killing a session can result in data loss or corruption, so make sure to first try and resolve the issue before using this command.

Diagnosing problematic queries

Before resorting to killing a session associated with a problematic query, it's important to diagnose the issue and try to resolve it. Here are some common techniques to diagnose problematic queries in Oracle:

  1. Use the EXPLAIN PLAN command to analyze the execution plan for the query. This can help you identify any performance issues and suggest possible ways to optimize the query.

  2. Use the SQL_TRACE parameter to trace SQL statements and identify any bottlenecks in the query execution.

  3. Monitor system resources to identify bottlenecks, such as CPU or I/O usage.

  4. Review log files to identify any errors or warnings that might be related to the query.

By using these techniques, you can diagnose the root cause of the issue and take appropriate actions to resolve it.

Conclusion

Terminating sessions by SQL ID in Oracle is a powerful tool to manage and troubleshoot system performance issues. With the information and code examples provided in this article, you should now have a deeper understanding of how to use SQL IDs and the ALTER SYSTEM KILL SESSION command to manage database sessions. Remember to use caution when using these tools and always remember to attempt to diagnose and resolve the issue before resorting to killing a session.

Popular questions

  1. What is an SQL ID in Oracle?
    Answer: An SQL ID is a unique identifier assigned to each SQL statement that is executed within the Oracle database.

  2. How can you find the SQL IDs for problematic queries in Oracle?
    Answer: You can use the V$SQL and V$SQLAREA views or the SQL_ID() function to find SQL IDs in Oracle.

  3. What is the ALTER SYSTEM KILL SESSION command used for in Oracle?
    Answer: The ALTER SYSTEM KILL SESSION command is used to terminate a user session in Oracle.

  4. When should you use caution when using the KILL SESSION command in Oracle?
    Answer: You should use caution when using the KILL SESSION command in Oracle as it can cause data loss or corruption if not used properly.

  5. What techniques can be used to diagnose problematic queries in Oracle before resorting to killing the associated session?
    Answer: Some common techniques used to diagnose problematic queries in Oracle include using the EXPLAIN PLAN command, tracing SQL statements with the SQL_TRACE parameter, monitoring system resources, and reviewing log files for errors or warnings.

Tag

"SessionKiller"

As an experienced software engineer, I have a strong background in the financial services industry. Throughout my career, I have honed my skills in a variety of areas, including public speaking, HTML, JavaScript, leadership, and React.js. My passion for software engineering stems from a desire to create innovative solutions that make a positive impact on the world. I hold a Bachelor of Technology in IT from Sri Ramakrishna Engineering College, which has provided me with a solid foundation in software engineering principles and practices. I am constantly seeking to expand my knowledge and stay up-to-date with the latest technologies in the field. In addition to my technical skills, I am a skilled public speaker and have a talent for presenting complex ideas in a clear and engaging manner. I believe that effective communication is essential to successful software engineering, and I strive to maintain open lines of communication with my team and clients.
Website https://www.linkedin.com/in/sricharan-s/
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