> ## 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.

# mutations_* session settings

> ClickHouse session settings in the mutations_* 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="mutations_max_literal_size_to_replace">
  mutations\_max\_literal\_size\_to\_replace
</h2>

<SettingsInfoBlock type="UInt64" default_value="16384" />

The maximum size of serialized literal in bytes to replace in `UPDATE` and `DELETE` queries. Takes effect only if at least one the two settings above is enabled. Default value: 16384 (16 KiB).

<h2 id="mutations_sync">
  mutations\_sync
</h2>

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

Allows to execute `ALTER TABLE ... UPDATE|DELETE|MATERIALIZE INDEX|MATERIALIZE PROJECTION|MATERIALIZE COLUMN|MATERIALIZE STATISTICS` queries ([mutations](/docs/reference/statements/alter/index#mutations)) synchronously.

Possible values:

| Value | Description                                                                                                                                            |
| ----- | ------------------------------------------------------------------------------------------------------------------------------------------------------ |
| `0`   | Mutations execute asynchronously.                                                                                                                      |
| `1`   | The query waits for all mutations to complete on the current server.                                                                                   |
| `2`   | The query waits for all mutations to complete on all replicas (if they exist).                                                                         |
| `3`   | The query waits only for active replicas. Supported only for `SharedMergeTree`. For `ReplicatedMergeTree` it behaves the same as `mutations_sync = 2`. |