> ## Documentation Index
> Fetch the complete documentation index at: https://clickhouse.com/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# max_concurrent_* 会话设置

> ClickHouse 在 max_concurrent_* 自动生成分组中的会话设置。

export const SettingsInfoBlock = ({type, default_value, changeable_without_restart}) => {
  return <div className="not-prose" style={{
    display: "flex",
    flexWrap: "wrap",
    alignItems: "baseline",
    columnGap: "0.5rem",
    rowGap: "0.125rem",
    margin: "0.375rem 0",
    fontSize: "0.8125rem",
    lineHeight: "1.125rem"
  }}>
      <div style={{
    fontWeight: 600,
    opacity: 0.72
  }}>类型</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{type}</div>
      <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>默认值</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{default_value}</div>
      {changeable_without_restart && <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>
          无需重启即可更改
        </div>}
      {changeable_without_restart && <div style={{
    overflowWrap: "anywhere"
  }}>
          {changeable_without_restart}
        </div>}
    </div>;
};

这些设置可在 [system.settings](/docs/zh/reference/system-tables/settings) 中查看，并由 [源代码](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp) 自动生成。

<div id="max_concurrent_queries_for_all_users">
  ## max\_concurrent\_queries\_for\_all\_users
</div>

<SettingsInfoBlock type="UInt64" default_value="0" />

如果此设置的值小于或等于当前正在同时处理的查询数量，则抛出异常。

示例：可将所有用户的 `max_concurrent_queries_for_all_users` 设置为 99，而数据库管理员可将自己的值设为 100，这样即使在 server 过载时，仍可运行查询进行调查。

修改某个查询或用户的此设置，不会影响其他查询。

可能的值：

* 正整数。
* 0 — 不限制。

**示例**

```xml theme={null}
<max_concurrent_queries_for_all_users>99</max_concurrent_queries_for_all_users>
```

**另请参见**

* [max\_concurrent\_queries](/docs/zh/reference/settings/server-settings/settings#max_concurrent_queries)

Cloud 默认值：`1000`。

<div id="max_concurrent_queries_for_user">
  ## max\_concurrent\_queries\_for\_user
</div>

<SettingsInfoBlock type="UInt64" default_value="0" />

每个用户可同时执行的查询最大数量。

可能的值：

* 正整数。
* 0 — 不限制。

**示例**

```xml theme={null}
<max_concurrent_queries_for_user>5</max_concurrent_queries_for_user>
```