Overview of the Performance Schema for Performance Insights on Amazon RDS for MariaDB or MySQL

The Performance Schema is an optional feature for monitoring Amazon RDS for MariaDB or MySQL runtime performance at a low level of detail. The Performance Schema is designed to have minimal impact on database performance. Performance Insights is a separate feature that you can use with or without the Performance Schema.

Topics

• Overview of the Performance Schema
• Performance Insights and the Performance Schema
• Automatic management of the Performance Schema by Performance Insights
• Effect of a reboot on the Performance Schema
• Determining whether Performance Insights is managing the Performance Schema
• Turn on the Performance Schema for Amazon RDS for MariaDB or MySQL

Overview of the Performance Schema

The Performance Schema monitors events in MariaDB and MySQL databases. An event is a database server action that consumes time and has been instrumented so that timing information can be collected. Examples of events include the following:

• Function calls

• Waits for the operating system

• Stages of SQL execution

• Groups of SQL statements

The PERFORMANCE_SCHEMA storage engine is a mechanism for implementing the Performance Schema feature. This engine collects event data using instrumentation in the database source code. The engine stores events in memory-only tables in the performance_schema database. You can query performance_schema just as you can query any other tables. For more information, see MySQL Performance Schema in the MySQL Reference Manual.

Performance Insights and the Performance Schema

Performance Insights and the Performance Schema are separate features, but they are connected. The behavior of Performance Insights for Amazon RDS for MariaDB or MySQL depends on whether the Performance Schema is turned on, and if so, whether Performance Insights manages the Performance Schema automatically. The following table describes the behavior.

Performance Schema turned on	Performance Insights management mode	Performance Insights behavior
Yes	Automatic	Collects detailed, low-level monitoring information Collects active session metrics every second Displays DB load categorized by detailed wait events, which you can use to identify bottlenecks
Yes	Manual	Collects wait events and per-SQL metrics Collects active session metrics every five seconds instead of every second Reports user states such as inserting and sending, which don't help you identify bottlenecks
No	N/A	Doesn't collect wait events, per-SQL metrics, or other detailed, low-level monitoring information Collects active session metrics every five seconds instead of every second Reports user states such as inserting and sending, which don't help you identify bottlenecks

Automatic management of the Performance Schema by Performance Insights

When you create an Amazon RDS for MariaDB or MySQL DB instance with Performance Insights turned on, the Performance Schema is also turned on. In this case, Performance Insights automatically manages your Performance Schema parameters. This is the recommended configuration.

When Performance Insights manages the Performance Schema automatically, the Source of performance_schema is System default.

Note

Automatic management of the Performance Schema isn't supported for the t4g.medium instance class.

If you change the performance_schema parameter value manually, and then later want to change to automatic management, see Turn on the Performance Schema for Amazon RDS for MariaDB or MySQL.

Important

When Performance Insights turns on the Performance Schema, it doesn't change the parameter group values. However, the values are changed on the DB instances that are running. The only way to see the changed values is to run the SHOW GLOBAL VARIABLES command.

Effect of a reboot on the Performance Schema

Performance Insights and the Performance Schema differ in their requirements for DB instance reboots:

Performance Schema

To turn this feature on or off, you must reboot the DB instance.

Performance Insights

To turn this feature on or off, you don't need to reboot the DB instance.

If the Performance Schema isn't currently turned on, and you turn on Performance Insights without rebooting the DB instance, the Performance Schema won't be turned on.