> ## 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.

# merges_mutations_* server settings

> ClickHouse server settings in the merges_mutations_* generated group.

These settings configure the ClickHouse server and are autogenerated from ClickHouse source.

## merges\_mutations\_memory\_usage\_soft\_limit

Type

UInt64

Default

0

Changeable without restart

No

Sets the limit on how much RAM is allowed to use for performing merge and mutation operations.
If ClickHouse reaches the limit set, it won't schedule any new background merge or mutation operations but will continue to execute already scheduled tasks.

> [!NOTE]
>
> A value of `0` means unlimited.

**Example**

```xml theme={null}
<merges_mutations_memory_usage_soft_limit>0</merges_mutations_memory_usage_soft_limit>
```

## merges\_mutations\_memory\_usage\_to\_ram\_ratio

Type

Double

Default

0.5

Changeable without restart

No

The default `merges_mutations_memory_usage_soft_limit` value is calculated as `memory_amount * merges_mutations_memory_usage_to_ram_ratio`.

**See also:**

* [max\_memory\_usage](/docs/reference/settings/session-settings/max-memory-usage.md#max_memory_usage)
* [merges\_mutations\_memory\_usage\_soft\_limit](/docs/reference/settings/server-settings/settings/merges-mutations.md#merges_mutations_memory_usage_soft_limit)