MySQL 5.6 Release Notes
MySQL account information is stored in the tables of the
mysql system database. This database and the
access control system are discussed extensively in
Chapter 5, MySQL Server Administration, which you should consult
for additional details.
Important
Some MySQL releases introduce changes to the grant tables to add new privileges or features. To make sure that you can take advantage of any new capabilities, update your grant tables to the current structure whenever you upgrade MySQL. See Section 2.11, “Upgrading MySQL”.
When the read_only system
variable is enabled, account-management statements require the
SUPER privilege, in addition to any
other required privileges. This is because they modify tables in
the mysql system database.