Identify and Optimize Resource-Intensive SQL Queries in Oracle

calendar Aug 28, 2024 · 3 min read · Oracle SQL Database Performance Optimization v$sqlarea  ·
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Pinpoint Resource-Hungry SQL in Oracle: A Performance Optimization Deep Dive

Purpose

This Oracle SQL query is your go-to tool for identifying SQL statements that are putting a strain on your database resources. By analyzing execution statistics, it highlights queries that are consuming significant disk reads and buffer gets, providing crucial insights for performance tuning and optimization.

Sample SQL Command

 1select sql_text
 2,      executions
 3,      to_char((((disk_reads+buffer_gets)/executions) * 8192)/1048576, '9,999,999,990.00')
 4	  as total_gets_per_exec_mb
 5,      to_char((( disk_reads             /executions) * 8192)/1048576, '9,999,999,990.00')
 6	  as disk_reads_per_exec_mb
 7,      to_char((( buffer_gets            /executions) * 8192)/1048576, '9,999,999,990.00')
 8	  as buffer_gets_per_exec_mb
 9,      parsing_user_id
10from   v$sqlarea
11where  executions > 10
12order by 6 desc
13/

Code Breakdown

  1. change 8192 to match block size: This initial comment serves as an important reminder to adjust the 8192 value in the subsequent calculations to match your database's actual block size.
  2. select sql_text, executions: Selects the following columns:
    • sql_text: Retrieves the actual text of the SQL statement.
    • executions: Shows the number of times the statement has been executed.
  3. to_char((((disk_reads+buffer_gets)/executions) * 8192)/1048576, '9,999,999,990.00') as total_gets_per_exec_mb: Calculates and formats the total data gets (disk reads + buffer gets) per execution in megabytes (MB).
  4. to_char((( disk_reads /executions) * 8192)/1048576, '9,999,999,990.00') as disk_reads_per_exec_mb: Calculates and formats the disk reads per execution in MB.
  5. to_char((( buffer_gets /executions) * 8192)/1048576, '9,999,999,990.00') as buffer_gets_per_exec_mb: Calculates and formats the buffer gets per execution in MB.
  6. parsing_user_id: Shows the ID of the user who parsed the SQL statement.
  7. from v$sqlarea: Queries the v$sqlarea dynamic performance view, which provides statistics about SQL statements currently in the shared SQL area.
  8. where executions > 10: Filters out SQL statements that have been executed less than 10 times, focusing on queries with a significant impact.
  9. order by 6 desc: Sorts the results in descending order based on the 6th column (total_gets_per_exec_mb), highlighting the most resource-intensive queries first.
  10. /: The forward slash is required in SQL*Plus or similar command-line tools to execute the query.

Key Points:

  • Resource Consumption Metrics: Calculates and displays key metrics like total data gets, disk reads, and buffer gets per execution, offering insights into resource usage.
  • Execution Frequency Filter: Focuses on queries with at least 10 executions to identify those with a substantial impact on the system.
  • Sorted Output: Presents the results in descending order of total data gets per execution, prioritizing the most resource-intensive queries.
  • Ensure you have the necessary privileges to access the v$sqlarea view.
  • Adjust the 8192 value in the calculations to match your database's block size for accurate results.
  • Consider using tools like Oracle Enterprise Manager or performance monitoring solutions for deeper analysis and visualization.

Insights:

  • Performance Bottleneck Identification: Helps pinpoint SQL statements causing performance issues due to excessive disk or buffer access.
  • Optimization Opportunities: Guides you towards queries that might benefit from tuning or optimization.
  • Resource Planning: Assists in capacity planning by highlighting queries contributing significantly to resource utilization.
  • By employing this query, you can proactively identify and address resource-intensive SQL statements, ensuring optimal performance and a smooth user experience in your Oracle database environment.

Explanations:

  • v$sqlarea: This dynamic performance view stores real-time statistics about SQL statements currently in the shared SQL area, including execution counts, disk reads, and buffer gets.
  • The calculations involving 8192 convert the block-based metrics (disk reads, buffer gets) into megabytes, making them easier to interpret.
  • to_char with the specified format mask ensures that the numerical results are displayed in a human-readable format with commas and decimal points.

References:

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