#### 27.12.14.1 Performance Schema persisted\_variables Table

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 The [`persisted_variables`](performance-schema-persisted-variables-table.html) table provides an SQL interface to the `mysqld-auto.cnf` file that stores persisted global system variable settings, enabling the file contents to be inspected at runtime using [`SELECT`](select.html) statements. Variables are persisted using [`SET PERSIST`](set-variable.html) or `PERSIST_ONLY` statements; see [Section 13.7.6.1, “SET Syntax for Variable Assignment”](set-variable.html). The table contains a row for each persisted system variable in the file. Variables not persisted do not appear in the table.

 For information about persisted system variables, see [Section 13.7.6.1, “SET Syntax for Variable Assignment”](set-variable.html).

 Suppose that `mysqld-auto.cnf` looks like this (slightly reformatted):

```
{
  "Version": 1,
  "mysql_server": {
    "max_connections": {
      "Value": "1000",
      "Metadata": {
        "Timestamp": 1.519921706e+15,
        "User": "root",
        "Host": "localhost"
      }
    },
    "autocommit": {
      "Value": "ON",
      "Metadata": {
        "Timestamp": 1.519921707e+15,
        "User": "root",
        "Host": "localhost"
      }
    }
  }
}
```

 Then [`persisted_variables`](performance-schema-persisted-variables-table.html) has these contents:

```
mysql> SELECT * FROM performance_schema.persisted_variables;
+-----------------+----------------+
| VARIABLE_NAME   | VARIABLE_VALUE |
+-----------------+----------------+
| autocommit      | ON             |
| max_connections | 1000           |
+-----------------+----------------+
```

 The [`persisted_variables`](performance-schema-persisted-variables-table.html) table has these columns:

* `VARIABLE_NAME`

   The variable name listed in `mysqld-auto.cnf`.

* `VARIABLE_VALUE`

   The value listed for the variable in `mysqld-auto.cnf`.

[`persisted_variables`](performance-schema-persisted-variables-table.html) has these indexes:

* Primary key on (`VARIABLE_NAME`)

[`TRUNCATE TABLE`](truncate-table.html) is not permitted for the [`persisted_variables`](performance-schema-persisted-variables-table.html) table.

