> ## 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.

# memory_* 会话设置

> 属于 memory_* 生成组的 ClickHouse 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，且由 [源代码](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp) 自动生成。

<div id="memory_tracker_fault_probability">
  ## memory\_tracker\_fault\_probability
</div>

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

用于测试 `exception safety`：在每次分配内存时，按指定概率抛出异常。

<div id="memory_usage_overcommit_max_wait_microseconds">
  ## memory\_usage\_overcommit\_max\_wait\_microseconds
</div>

<SettingsInfoBlock type="UInt64" default_value="5000000" />

在用户级别发生内存 overcommit 时，线程等待内存释放的最长时间。
如果达到 timeout 且内存仍未释放，则会抛出异常。
有关 [memory overcommit](/docs/zh/concepts/features/configuration/settings/memory-overcommit) 的更多信息，请参阅。