You can use the diagnostics feature to identify performance issues of your databases.


  • Database Autonomy Service (DAS) provides the diagnostics feature only for the following types of database instances:
    • MySQL
    • ApsaraDB RDS for PostgreSQL
    • PolarDB for PostgreSQL
  • The database instance is connected to DAS. For more information, see Access instances.


  1. Log on to the DAS console.
  2. In the left-side navigation pane, click Instance Monitoring.
  3. On the page that appears, find a database instance and click the instance ID. The instance details page appears.
  4. In the left-side navigation pane, click Diagnostics.
  5. On the Diagnostics page, you can create diagnostic reports and view previous reports.


  • Q: How are the thread usage, connection usage, and maximum number of threads of a session calculated?
    A: These metrics for ApsaraDB RDS for MySQL instances and PolarDB for MySQL clusters are calculated based on the following formulas:
    • Thread usage = Number of active threads/Maximum number of threads
    • Connection usage = Current number of connections/Maximum number of connections allowed by the instance type
    • Maximum number of threads = thread_pool_size × (thread_pool_oversubscribe + 1)
  • Q: Why does the thread usage exceed 100%?

    A: According to the formula for thread usage, when the number of active threads is larger than the maximum number of threads, the thread usage exceeds 100%. The thread pool implementation method of ApsaraDB RDS for MySQL does not limit the number of active threads. Therefore, the number of active threads may be more than the maximum number of threads.

Related API operations


Learn more

For more information about the automatic SQL diagnostics feature, see Cost-based SQL diagnostics engine.