docs/_docs/developers-guide/sql/system-views.adoc

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= System Views

Ignite provides a number of built-in SQL views that provide information on the cluster's state and provide real-time insight into the status of its components. These views are available in the SYSTEM schema.

== Getting Data

You access system views in Ignite by using SQL and selecting data from the system view like you would from any other table.  For example, you can get a list of all available system views in the following way:

[source, sql]
----
SELECT id, schema, name FROM system.system_views WHERE type = 'NODE'
----

You can also use joins to combine data from multiple views. The example below returns all columns of a view that was found in the `SYSTEM_VIEWS` view:

[source, sql]
----
SELECT svc.*
  FROM system.system_view_columns svc
  JOIN system.system_views sv ON svc.view_id = sv.id
 WHERE sv.name = 'SYSTEM_VIEWS'
----

== Available Views

=== SYSTEM_VIEWS

Describes available system views.

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|=======
|Column	|Data Type| Description

| ID | INT32 | System view ID.
| SCHEMA | STRING | Name of the schema used. Default is `SYSTEM`.
| NAME | STRING | System view name.
| TYPE | STRING | System view type. Possible values:

* NODE - The view provides node-specific information. Data will be collected from all nodes, and represented in the view.
* CLUSTER - The view provides cluster-wide information. Data will be collected from one node, chosen to represent the cluster.

|=======

=== SYSTEM_VIEW_COLUMNS

Describes available system view columns.

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|=======
|Column	|Data Type| Description

| VIEW_ID | INT32 | System view ID.
| NAME | STRING | Column name.
| TYPE | STRING | Column type. Can by any of the link:sql-reference/data-types[supported types].
| NULLABLE | BOOLEAN |Defines if the column can be empty.
| PRECISION | INT32 |Maximum number of digits.
| SCALE | INT32 |Maximum number of decimal places.
| LENGTH | INT32 |Maximum length of the value. Symbols for string values or bytes for binary values.

|=======

=== SYSTEM.ZONES

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|=======
|Column	|Data Type| Description

| NAME | STRING | The name of the distribution zone.
| PARTITIONS | INT32 | The number of partitions in the distribution zone.
| REPLICAS | STRING |The number of copies of each partition in the distribution zone.
| DATA_NODES_AUTO_ADJUST_SCALE_UP | INT32 | The delay in seconds between the new node joining and the start of data zone adjustment.
| DATA_NODES_AUTO_ADJUST_SCALE_DOWN | INT32 | The delay in seconds between the node leaving the cluster and the start of data zone adjustment.
| DATA_NODES_FILTER | STRING | The filter that specifies what nodes will be used by the distribution zone.
| IS_DEFAULT_ZONE | BOOLEAN | Defines if the data zone is used by default.

|=======