> ## 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.

# skip_unavailable_shards_* session settings

> ClickHouse session settings in the skip_unavailable_shards_* 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="skip_unavailable_shards">
  skip\_unavailable\_shards
</h2>

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

Enables or disables silently skipping of unavailable shards.

The behavior of this setting is controlled by the `skip_unavailable_shards_mode` parameter.

Possible values:

* 1 — skipping enabled.

  If a shard is unavailable, ClickHouse returns a result based on partial data and does not report node availability issues.

* 0 — skipping disabled.

  If a shard is unavailable, ClickHouse throws an exception.

<h2 id="skip_unavailable_shards_mode">
  skip\_unavailable\_shards\_mode
</h2>

<SettingsInfoBlock type="SkipUnavailableShardsMode" default_value="unavailable_or_table_missing" />

<VersionHistory rows={[{"id": "row-1","items": [{"label": "26.7"},{"label": "unavailable_or_table_missing"},{"label": "New setting to control which exceptions from a remote shard are ignored when `skip_unavailable_shards` is enabled. The default matches the historical behavior: a shard whose table is missing is treated as unavailable."}]}]} />

Controls which exceptions from a remote shard are silently ignored when `skip_unavailable_shards` is enabled. The setting has no effect when `skip_unavailable_shards = 0`.

Possible values:

* `unavailable` — Only connection-related errors are ignored. A shard is considered unavailable when ClickHouse cannot connect to any of its replicas, or when a replica's hostname cannot be resolved through DNS.

* `unavailable_or_table_missing` — In addition to `unavailable`, errors caused by a missing table or database on the shard are ignored. This is useful while a table is being created or dropped across a cluster. This is the default and matches the historical behavior of `skip_unavailable_shards`, which also treated a shard whose table does not exist as unavailable.

* `unavailable_or_exception_before_processing` — In addition to `unavailable`, any exception received from a shard before it returned any data block to the initiator is ignored. An exception that arrives after the shard already returned some data is always rethrown. Note that "before it returned any data" is checked at the initiator: a shard that performs a blocking computation (for example an aggregation, sort, or `LIMIT BY`) may process rows and fail before emitting any block, in which case its partial work is silently discarded and the query returns a result built from the remaining shards. This is therefore the most permissive mode and should be used with care.