> ## 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.

# async_load_* server settings

> ClickHouse server settings in the async_load_* 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 configure the ClickHouse server and are autogenerated from ClickHouse source.

<h2 id="async_load_databases">
  async\_load\_databases
</h2>

<SettingsInfoBlock type="Bool" default_value="1" changeable_without_restart="No" />

Asynchronous loading of databases and tables.

* If `true` all non-system databases with `Ordinary`, `Atomic` and `Replicated` engine will be loaded asynchronously after the ClickHouse server start up. See `system.asynchronous_loader` table, `tables_loader_background_pool_size` and `tables_loader_foreground_pool_size` server settings. Any query that tries to access a table, that is not yet loaded, will wait for exactly this table to be started up. If load job fails, query will rethrow an error (instead of shutting down the whole server in case of `async_load_databases = false`). The table that is waited for by at least one query will be loaded with higher priority. DDL queries on a database will wait for exactly that database to be started up. Also consider setting a limit `max_waiting_queries` for the total number of waiting queries.
* If `false`, all databases are loaded when the server starts.

**Example**

```xml theme={null}
<async_load_databases>true</async_load_databases>
```

<h2 id="async_load_system_database">
  async\_load\_system\_database
</h2>

<SettingsInfoBlock type="Bool" default_value="0" changeable_without_restart="No" />

Asynchronous loading of system tables. Helpful if there is a high amount of log tables and parts in the `system` database. Independent of the `async_load_databases` setting.

* If set to `true`, all system databases with `Ordinary`, `Atomic`, and `Replicated` engines will be loaded asynchronously after the ClickHouse server starts. See `system.asynchronous_loader` table, `tables_loader_background_pool_size` and `tables_loader_foreground_pool_size` server settings. Any query that tries to access a system table, that is not yet loaded, will wait for exactly this table to be started up. The table that is waited for by at least one query will be loaded with higher priority. Also consider setting the `max_waiting_queries` setting to limit the total number of waiting queries.
* If set to `false`, system database loads before server start.

**Example**

```xml theme={null}
<async_load_system_database>true</async_load_system_database>
```