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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.