> ## 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.

# read_backoff_* session settings

> ClickHouse session settings in the read_backoff_* generated group.

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
  }}>Type</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{type}</div>
      <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>Default</div>
      <div style={{
    overflowWrap: "anywhere"
  }}>{default_value}</div>
      {changeable_without_restart && <div style={{
    fontWeight: 600,
    opacity: 0.72,
    marginInlineStart: "0.5rem"
  }}>
          Changeable without restart
        </div>}
      {changeable_without_restart && <div style={{
    overflowWrap: "anywhere"
  }}>
          {changeable_without_restart}
        </div>}
    </div>;
};

These settings are available in [system.settings](/docs/reference/system-tables/settings) and are autogenerated from [source](https://github.com/ClickHouse/ClickHouse/blob/master/src/Core/Settings.cpp).

<h2 id="read_backoff_max_throughput">
  read\_backoff\_max\_throughput
</h2>

<SettingsInfoBlock type="UInt64" default_value="1048576" />

Settings to reduce the number of threads in case of slow reads. Count events when the read bandwidth is less than that many bytes per second.

<h2 id="read_backoff_min_concurrency">
  read\_backoff\_min\_concurrency
</h2>

<SettingsInfoBlock type="UInt64" default_value="1" />

Settings to try keeping the minimal number of threads in case of slow reads.

<h2 id="read_backoff_min_events">
  read\_backoff\_min\_events
</h2>

<SettingsInfoBlock type="UInt64" default_value="2" />

Settings to reduce the number of threads in case of slow reads. The number of events after which the number of threads will be reduced.

<h2 id="read_backoff_min_interval_between_events_ms">
  read\_backoff\_min\_interval\_between\_events\_ms
</h2>

<SettingsInfoBlock type="Milliseconds" default_value="1000" />

Settings to reduce the number of threads in case of slow reads. Do not pay attention to the event, if the previous one has passed less than a certain amount of time.

<h2 id="read_backoff_min_latency_ms">
  read\_backoff\_min\_latency\_ms
</h2>

<SettingsInfoBlock type="Milliseconds" default_value="1000" />

Setting to reduce the number of threads in case of slow reads. Pay attention only to reads that took at least that much time.