### 15.17.2 Enabling InnoDB Monitors

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 When `InnoDB` monitors are enabled for periodic output, `InnoDB` writes the output to [**mysqld**](mysqld.html) server standard error output (`stderr`) every 15 seconds, approximately.

`InnoDB` sends the monitor output to `stderr` rather than to `stdout` or fixed-size memory buffers to avoid potential buffer overflows.

 On Windows, `stderr` is directed to the default log file unless configured otherwise. If you want to direct the output to the console window rather than to the error log, start the server from a command prompt in a console window with the [`--console`](server-options.html#option_mysqld_console) option. For more information, see [Default Error Log Destination on Windows](error-log-destination-configuration.html#error-log-destination-configuration-windows).

 On Unix and Unix-like systems, `stderr` is typically directed to the terminal unless configured otherwise. For more information, see [Default Error Log Destination on Unix and Unix-Like Systems](error-log-destination-configuration.html#error-log-destination-configuration-unix).

`InnoDB` monitors should only be enabled when you actually want to see monitor information because output generation causes some performance decrement. Also, if monitor output is directed to the error log, the log may become quite large if you forget to disable the monitor later.

Note

 To assist with troubleshooting, `InnoDB` temporarily enables standard `InnoDB` Monitor output under certain conditions. For more information, see [Section 15.21, “InnoDB Troubleshooting”](innodb-troubleshooting.html).

`InnoDB` monitor output begins with a header containing a timestamp and the monitor name. For example:

```
=====================================
2014-10-16 18:37:29 0x7fc2a95c1700 INNODB MONITOR OUTPUT
=====================================
```

 The header for the standard `InnoDB` Monitor (`INNODB MONITOR OUTPUT`) is also used for the Lock Monitor because the latter produces the same output with the addition of extra lock information.

 The [`innodb_status_output`](innodb-parameters.html#sysvar_innodb_status_output) and [`innodb_status_output_locks`](innodb-parameters.html#sysvar_innodb_status_output_locks) system variables are used to enable the standard `InnoDB` Monitor and `InnoDB` Lock Monitor.

 The [`PROCESS`](privileges-provided.html#priv_process) privilege is required to enable or disable `InnoDB` Monitors.

#### Enabling the Standard InnoDB Monitor

 Enable the standard `InnoDB` Monitor by setting the [`innodb_status_output`](innodb-parameters.html#sysvar_innodb_status_output) system variable to `ON`.

```
SET GLOBAL innodb_status_output=ON;
```

 To disable the standard `InnoDB` Monitor, set [`innodb_status_output`](innodb-parameters.html#sysvar_innodb_status_output) to `OFF`.

 When you shut down the server, the [`innodb_status_output`](innodb-parameters.html#sysvar_innodb_status_output) variable is set to the default `OFF` value.

#### Enabling the InnoDB Lock Monitor

`InnoDB` Lock Monitor data is printed with the `InnoDB` Standard Monitor output. Both the `InnoDB` Standard Monitor and `InnoDB` Lock Monitor must be enabled to have `InnoDB` Lock Monitor data printed periodically.

 To enable the `InnoDB` Lock Monitor, set the [`innodb_status_output_locks`](innodb-parameters.html#sysvar_innodb_status_output_locks) system variable to `ON`. Both the `InnoDB` standard Monitor and `InnoDB` Lock Monitor must be enabled to have `InnoDB` Lock Monitor data printed periodically:

```
SET GLOBAL innodb_status_output=ON;
SET GLOBAL innodb_status_output_locks=ON;
```

 To disable the `InnoDB` Lock Monitor, set [`innodb_status_output_locks`](innodb-parameters.html#sysvar_innodb_status_output_locks) to `OFF`. Set [`innodb_status_output`](innodb-parameters.html#sysvar_innodb_status_output) to `OFF` to also disable the `InnoDB` Standard Monitor.

 When you shut down the server, the [`innodb_status_output`](innodb-parameters.html#sysvar_innodb_status_output) and [`innodb_status_output_locks`](innodb-parameters.html#sysvar_innodb_status_output_locks) variables are set to the default `OFF` value.

Note

 To enable the `InnoDB` Lock Monitor for [`SHOW ENGINE INNODB STATUS`](show-engine.html) output, you are only required to enable [`innodb_status_output_locks`](innodb-parameters.html#sysvar_innodb_status_output_locks).

#### Obtaining Standard InnoDB Monitor Output On Demand

 As an alternative to enabling the standard `InnoDB` Monitor for periodic output, you can obtain standard `InnoDB` Monitor output on demand using the [`SHOW ENGINE INNODB STATUS`](show-engine.html) SQL statement, which fetches the output to your client program. If you are using the [**mysql**](mysql.html) interactive client, the output is more readable if you replace the usual semicolon statement terminator with `\G`:

```
mysql> SHOW ENGINE INNODB STATUS\G
```

[`SHOW ENGINE INNODB STATUS`](show-engine.html) output also includes `InnoDB` Lock Monitor data if the `InnoDB` Lock Monitor is enabled.

#### Directing Standard InnoDB Monitor Output to a Status File

 Standard `InnoDB` Monitor output can be enabled and directed to a status file by specifying the `--innodb-status-file` option at startup. When this option is used, `InnoDB` creates a file named `innodb_status.*`pid`*` in the data directory and writes output to it every 15 seconds, approximately.

`InnoDB` removes the status file when the server is shut down normally. If an abnormal shutdown occurs, the status file may have to be removed manually.

 The `--innodb-status-file` option is intended for temporary use, as output generation can affect performance, and the `innodb_status.*`pid`*` file can become quite large over time.

