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RESET PERSIST  affects the contents of the Performance Schema persisted_variables  table because the table contents correspond to the contents of the mysqld-auto.cnf  file. On the other hand, because RESET PERSIST  does not change variable values, it has no effect on the contents of the Performance Schema variables_info  table until the server is restarted. 

For information about RESET  statement variants that clear the state of other server operations, see Section 13.7.8.6, “RESET Statement” . 

## 13.7.8.8 RESTART Statement 

RESTART 

This statement stops and restarts the MySQL server. It requires the SHUTDOWN  privilege. 

One use for RESTART  is when it is not possible or convenient to gain command-line access to the MySQL server on the server host to restart it. For example, SET PERSIST_ONLY  can be used at runtime to make configuration changes to system variables that can be set only at server startup, but the server must still be restarted for those changes to take effect. The RESTART  statement provides a way to do so from within client sessions, without requiring command-line access on the server host. 

<img src='content_image/774669.jpg'>

## Note 

After executing a RESTART  statement, the client can expect the current connection to be lost. If auto-reconnect is enabled, the connection is reestablished after the server restarts. Otherwise, the connection must be reestablished manually. 

A successful RESTART  operation requires mysqld  to be running in an environment that has a monitoring process available to detect a server shutdown performed for restart purposes: 

•In the presence of a monitoring process, RESTART  causes mysqld  to terminate such that the monitoring process can determine that it should start a new mysqld  instance. 

•If no monitoring process is present, RESTART  fails with an error. 

These platforms provide the necessary monitoring support for the RESTART  statement: 

•Windows, when mysqld  is started as a Windows service or standalone. ( mysqld  forks, and one process acts as a monitor to the other, which acts as the server.) 

•Unix and Unix-like systems that use systemd or mysqld_safe  to manage mysqld . 

To configure a monitoring environment such that mysqld  enables the RESTART  statement: 

1. Set the MYSQLD_PARENT_PID  environment variable to the value of the process ID of the process that starts mysqld , before starting mysqld . 

2. When mysqld  performs a shutdown due to use of the RESTART  statement, it returns exit code 16. 

3. When the monitoring process detects an exit code of 16, it starts mysqld  again. Otherwise, it exits. 

Here is a minimal example as implemented in the bash  shell: 

#!/bin/bash export MYSQLD_PARENT_PID=$$ export MYSQLD_RESTART_EXIT=16 

