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This variable is the user interface to the Debug Sync facility. Use of Debug Sync requires that MySQL be configured with the -DENABLE_DEBUG_SYNC=1 CMake  option (see Section 2.9.7, “MySQL Source- Configuration Options” ). If Debug Sync is not compiled in, this system variable is not available. 

The global variable value is read only and indicates whether the facility is enabled. By default, Debug Sync is disabled and the value of debug_sync  is OFF . If the server is started with --debug-sync- timeout= N , where N  is a timeout value greater than 0, Debug Sync is enabled and the value of debug_sync  is ON - current signal  followed by the signal name. Also, N  becomes the default timeout for individual synchronization points. 

The session value can be read by any user and has the same value as the global variable. The session value can be set to control synchronization points. 

Setting the session value of this system variable is a restricted operation. The session user must have privileges sufficient to set restricted session variables. See Section 5.1.9.1, “System Variable Privileges” . 

For a description of the Debug Sync facility and how to use synchronization points, see MySQL Internals: Test Synchronization. 

• default_authentication_plugin 

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The default authentication plugin. These values are permitted: 

• mysql_native_password : Use MySQL native passwords; see Section 6.4.1.1, “Native Pluggable Authentication” . 

• sha256_password : Use SHA-256 passwords; see Section 6.4.1.3, “SHA-256 Pluggable Authentication” . 

