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## Chapter 28 MySQL sys Schema 

## Table of Contents 

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MySQL 8.0 includes the sys  schema, a set of objects that helps DBAs and developers interpret data collected by the Performance Schema. sys  schema objects can be used for typical tuning and diagnosis use cases. Objects in this schema include: 

•Views that summarize Performance Schema data into more easily understandable form. 

•Stored procedures that perform operations such as Performance Schema configuration and generating diagnostic reports. 

•Stored functions that query Performance Schema configuration and provide formatting services. 

For new installations, the sys  schema is installed by default during data directory initialization if you use mysqld  with the --initialize  or --initialize-insecure  option. If this is not desired, you can drop the sys  schema manually after initialization if it is unneeded. 

The MySQL upgrade procedure produces an error if a sys  schema exists but has no version  view, on the assumption that absence of this view indicates a user-created sys  schema. To upgrade in this case, remove or rename the existing sys  schema first. 

sys  schema objects have a DEFINER  of ’mysql.sys’@’localhost’ . Use of the dedicated mysql.sys account avoids problems that occur if a DBA renames or removes the root  account. 

## 28.1 Prerequisites for Using the sys Schema 

Before using the sys  schema, the prerequisites described in this section must be satisfied. 

Because the sys  schema provides an alternative means of accessing the Performance Schema, the Performance Schema must be enabled for the sys  schema to work. See Section 27.3, “Performance Schema Startup Configuration” . 

For full access to the sys  schema, a user must have these privileges: 

• SELECT  on all sys  tables and views 

• EXECUTE  on all sys  stored procedures and functions 

• INSERT  and UPDATE  for the sys_config  table, if changes are to be made to it 

•Additional privileges for certain sys  schema stored procedures and functions, as noted in their descriptions (for example, the ps_setup_save()  procedure) 

