> ## 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_bytes_* MergeTree table settings

> ClickHouse MergeTree table settings in the max_bytes_* 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.merge\_tree\_settings](/docs/reference/system-tables/merge_tree_settings) and are autogenerated from ClickHouse source.

<h2 id="max_bytes_to_merge_at_max_space_in_pool">
  max\_bytes\_to\_merge\_at\_max\_space\_in\_pool
</h2>

<SettingsInfoBlock type="UInt64" default_value="161061273600" />

The maximum total parts size (in bytes) to be merged into one part, if there
are enough resources available. Corresponds roughly to the maximum possible
part size created by an automatic background merge. (0 means merges will be disabled)

Possible values:

* Any non-negative integer.

The merge scheduler periodically analyzes the sizes and number of parts in
partitions, and if there are enough free resources in the pool, it starts
background merges. Merges occur until the total size of the source parts is
larger than `max_bytes_to_merge_at_max_space_in_pool`.

Merges initiated by [OPTIMIZE FINAL](/docs/reference/statements/optimize)
ignore `max_bytes_to_merge_at_max_space_in_pool` (only the free disk space
is taken into account).

<h2 id="max_bytes_to_merge_at_min_space_in_pool">
  max\_bytes\_to\_merge\_at\_min\_space\_in\_pool
</h2>

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

The maximum total part size (in bytes) to be merged into one part, with the
minimum available resources in the background pool.

Possible values:

* Any positive integer.

`max_bytes_to_merge_at_min_space_in_pool` defines the maximum total size of
parts which can be merged despite the lack of available disk space (in pool).
This is necessary to reduce the number of small parts and the chance of
`Too many parts` errors.
Merges book disk space by doubling the total merged parts sizes.
Thus, with a small amount of free disk space, a situation may occur in which
there is free space, but this space is already booked by ongoing large merges,
so other merges are unable to start, and the number of small parts grows
with every insert.