In the previous article, I have shared basic about the Performance Schema of MySQL.

MySQL 5.5: Introduced PERFORMANCE_SCHEMA storage engine to inspect the performance data

In this post, I am sharing basic command and configuration of Performance Schema.

Using below command, You can find performance_schema is enabled or disabled.

SHOW VARIABLES LIKE 'performance_schema';
+--------------------+-------+
| Variable_name      | Value |
+--------------------+-------+
| performance_schema | ON    |
+--------------------+-------+

It is enabled by default, but in the case of any reason if it is not enabled, open your my.cnf or my.ini file and put below parameter value.

[mysqld]
performance_schema=ON

Now It requires restarting the MySQL service because this server parameter enables at server startup.
Using below query, You can also check MySQL database engine information.

SELECT * 
FROM INFORMATION_SCHEMA.ENGINES;

After enable, You can use this schema:

USE performance_schema;

Find out all tables of the Performance Schema:

SHOW TABLES;

Some of the important tables are:

SELECT * FROM events_waits_current; -- To see what the server is doing at the moment
SELECT * FROM file_instances; --  To get instances of instruments for file I/O operations and their associated files

Performance schema has also few parameter tables like instruments and staging:

The Performance Schema instruments stages, which are steps during the statement-execution process, such as parsing a statement, opening a table, or performing a file sort operation.

Stages correspond to the thread states displayed by SHOW PROCESSLIST or that are visible in the INFORMATION_SCHEMA.PROCESSLIST table. Stages begin and end when state values change.

Performance schema setup_instruments table:

SELECT * FROM setup_instruments 
WHERE NAME RLIKE 'stage/sql/[a-c]';

Example to enable one of parameter:

UPDATE setup_instruments SET ENABLED = 'YES', TIMED = 'YES'
WHERE NAME = 'stage/sql/altering table';

Peformance schema setup_consumers table:

SELECT * FROM setup_consumers 
WHERE NAME LIKE '%stages%';

Example to enable one parameter:

UPDATE setup_consumers SET ENABLED ='YES' 
WHERE NAME = 'events_stages_current';

Before starting to database performance tuning activities, Database Administrator requires different types of statistics like wait events, connection time, instance information, lock tables.

MySQL 5.5 introduced a PERFORMANCE_SCHEMA storage engine to monitor the performance of data and different types of server events.
One performance_schema database is created under the PERFORMANCE_SCHEMA storage engine.

An INFORMATION_SCHEMA focuses on METADATA information, but PERFORMANCE_SCHEMA primary focuses on MySQL Database Performance related Data.

The Performance Schema is also collecting different types of MySQL Server event with the related time information.
It stores all collected information in the table so that we can easily access it.

The Performance Schema events are specific to an instance of MySQL Server and changes are not written to the binary log.

We can set enable or disable PERFORMANCE_SCHEMA storage engine. Once it enables, it collects and monitors the different performance related event stats.

The main advantage of Performance Schema is, it never changes the server behaviour and never disturb to Query Planner for making a Query Execution Plan.

The execution of server proceeds normally even if the Performance Schema fails internally.

Please visit the next article about, How to configure Performance Schema and basic usage of it.