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title ALTER DATABASE (Parallel Data Warehouse) | Microsoft Docs
ms.custom
ms.date 06/28/2018
ms.prod sql
ms.prod_service pdw
ms.reviewer
ms.suite sql
ms.technology t-sql
ms.tgt_pltfrm
ms.topic conceptual
ms.assetid 5751656b-7aae-4152-a314-4c631bea4fc4
caps.latest.revision 10
author CarlRabeler
ms.author carlrab
manager craigg
monikerRange >= aps-pdw-2016 || = sqlallproducts-allversions

ALTER DATABASE (Parallel Data Warehouse)

[!INCLUDEtsql-appliesto-xxxxxx-xxxx-xxxx-pdw-md]

Modifies the maximum database size options for replicated tables, distributed tables, and the transaction login [!INCLUDEssPDW]. Use this statement to manage disk space allocations for a database as it grows or shrinks in size.

This article also describes syntax related to setting database options in Parallel Data Warehouse.

Article link icon Transact-SQL Syntax Conventions (Transact-SQL)

::: moniker range="= aps-pdw-2016 || = sqlallproducts-allversions"

Syntax for APS 2016-AU6

-- Parallel Data Warehouse  
ALTER DATABASE database_name    
    SET ( <set_database_options>   | <db_encryption_option> )  
[;]  
  
<set_database_options> ::=   
{  
    AUTOGROW = { ON | OFF }  
    | REPLICATED_SIZE = size [GB]  
    | DISTRIBUTED_SIZE = size [GB]  
    | LOG_SIZE = size [GB]
}  
  
<db_encryption_option> ::=  
    ENCRYPTION { ON | OFF }

::: moniker-end ::: moniker range=">= aps-pdw-2016-au7 || = sqlallproducts-allversions"

Syntax starting in APS 2016-AU7

-- Parallel Data Warehouse  
ALTER DATABASE database_name    
    SET ( <set_database_options>   | <db_encryption_option> )  
[;]  
  
<set_database_options> ::=   
{  
    AUTOGROW = { ON | OFF }  
    | REPLICATED_SIZE = size [GB]  
    | DISTRIBUTED_SIZE = size [GB]  
    | LOG_SIZE = size [GB]
    | SET AUTO_CREATE_STATISTICS { ON | OFF }
    | SET AUTO_UPDATE_STATISTICS { ON | OFF } 
    | SET AUTO_UPDATE_STATISTICS_ASYNC { ON | OFF }
}  
  
<db_encryption_option> ::=  
    ENCRYPTION { ON | OFF }

::: moniker-end

Arguments

database_name
The name of the database to be modified. To display a list of databases on the appliance, use sys.databases (Transact-SQL).

AUTOGROW = { ON | OFF }
Updates the AUTOGROW option. When AUTOGROW is ON, [!INCLUDEssPDW] automatically increases the amount of space set aside for replicated tables, distributed tables, and the transaction log, when more space is needed. When AUTOGROW is OFF, [!INCLUDEssPDW] returns an error if replicated tables, distributed tables, or the transaction log sizes are larger than the largest amount allowed by the size setting.

REPLICATED_SIZE = size [GB]
Specifies the new max gigabytes per Compute node. A node is used for storing all of the replicated tables in the database being altered. If you are planning for appliance storage space, you will need to multiply REPLICATED_SIZE by the number of Compute nodes in the appliance.

DISTRIBUTED_SIZE = size [GB]
Specifies the new max gigabytes per database for storing all of the distributed tables in the database being altered. The size is distributed across all of the Compute nodes in the appliance.

LOG_SIZE = size [GB]
Specifies the new max gigabytes per database for storing all of the transaction logs in the database being altered. The size is distributed across all of the Compute nodes in the appliance.

ENCRYPTION { ON | OFF }
Sets the database to be encrypted (ON) or not encrypted (OFF). Encryption can only be configured for [!INCLUDEssPDW] when sp_pdw_database_encryption has been set to 1. A database encryption key must be created before transparent data encryption can be configured. For more information about database encryption, see Transparent Data Encryption (TDE).

::: moniker range=">= aps-pdw-2016-au7 || = sqlallproducts-allversions" SET AUTO_CREATE_STATISTICS { ON | OFF } When this setting is ON, the query optimizer automatically creates statistics on individual columns in the query predicate. The optimizer thereby improves the cardinality estimates for the query plan. These single-column statistics are created on columns that do not already have a histogram in an existing statistics object.

The default is ON for new databases created after upgrading to APS AU7. The default is OFF for databases that are created before the upgrade is applied.

For more information about statistics, see Statistics

SET AUTO_UPDATE_STATISTICS { ON | OFF } When this setting is ON, the query optimizer determines when statistics might be out-of-date. The optimizer then updates the statistics when they are used by a query. Statistics become outdated after the operations of INSERT, UPDATE, DELETE, or MERGE change the data distribution in the table or indexed view. The query optimizer determines when statistics might be outdated by counting the number of data modifications since the latest statistics update, and then comparing a threshold to the number of modifications. The threshold is based on the number of rows in the table or indexed view.

The default is ON for new databases created after upgrading to APS AU7. The default is OFF for databases created prior to the upgrade.

For more information about statistics, see Statistics.

SET AUTO_UPDATE_STATISTICS_ASYNC { ON | OFF } This asynchronous statistics update option controls whether the query optimizer uses synchronous or asynchronous statistics updates. The option applies to the following items:

  • Statistics objects created for indexes.
  • Single columns in query predicates.
  • Statistics created with the CREATE STATISTICS statement.

The default is ON for new databases created after upgrading to APS AU7. The default is OFF for databases created prior to the upgrade.

For more information about statistics, see Statistics. ::: moniker-end

Permissions

Requires the ALTER permission on the database.

Error Messages

If auto-stats is disabled, and you try to alter the statistics settings, PDW gives an error. The error says "This option is not supported in PDW." The system administrator can enable auto-stats by enabling the feature switch AutoStatsEnabled.

General Remarks

The values for REPLICATED_SIZE, DISTRIBUTED_SIZE, and LOG_SIZE can be greater than, equal to, or less than the current values for the database.

Limitations and Restrictions

Grow and shrink operations are approximate. The resulting actual sizes can vary from the size parameters.

[!INCLUDEssPDW] does not handle the ALTER DATABASE statement as an atomic operation. If the statement is aborted during execution, changes that have already occurred will still exist.

::: moniker range=">= aps-pdw-2016-au7 || = sqlallproducts-allversions" The statistics settings only work if the administrator has enable auto-stats. If you are an administrator, use the feature switch AutoStatsEnabled to enable or disable auto-stats. ::: moniker-end

Locking Behavior

Takes a shared lock on the DATABASE object. While another user is using a given database for reading or writer, you cannot alter the database. This restriction includes sessions that have issued a USE statement on the database.

Performance

Shrinking a database can take a large amount of time and system resources. Factors include the size of the actual data within the database, and the amount of fragmentation on disk. For example, shrinking a database could take several hours or more.

Determining Encryption Progress

Use the following query to determine progress of database transparent data encryption as a percent.

WITH  
database_dek AS (  
    SELECT ISNULL(db_map.database_id, dek.database_id) AS database_id,  
        dek.encryption_state, dek.percent_complete,  
        dek.key_algorithm, dek.key_length, dek.encryptor_thumbprint,  
        type  
    FROM sys.dm_pdw_nodes_database_encryption_keys AS dek  
    INNER JOIN sys.pdw_nodes_pdw_physical_databases AS node_db_map  
        ON dek.database_id = node_db_map.database_id   
        AND dek.pdw_node_id = node_db_map.pdw_node_id  
    LEFT JOIN sys.pdw_database_mappings AS db_map  
        ON node_db_map .physical_name = db_map.physical_name  
    INNER JOIN sys.dm_pdw_nodes nodes  
        ON nodes.pdw_node_id = dek.pdw_node_id  
    WHERE dek.encryptor_thumbprint <> 0x  
),  
dek_percent_complete AS (  
    SELECT database_dek.database_id, AVG(database_dek.percent_complete) AS percent_complete  
    FROM database_dek  
    WHERE type = 'COMPUTE'  
    GROUP BY database_dek.database_id  
)  
SELECT DB_NAME( database_dek.database_id ) AS name,  
    database_dek.database_id,  
    ISNULL(  
       (SELECT TOP 1 dek_encryption_state.encryption_state  
        FROM database_dek AS dek_encryption_state  
        WHERE dek_encryption_state.database_id = database_dek.database_id  
        ORDER BY (CASE encryption_state  
            WHEN 3 THEN -1  
            ELSE encryption_state  
            END) DESC), 0)  
        AS encryption_state,  
dek_percent_complete.percent_complete,  
database_dek.key_algorithm, database_dek.key_length, database_dek.encryptor_thumbprint  
FROM database_dek  
INNER JOIN dek_percent_complete   
    ON dek_percent_complete.database_id = database_dek.database_id  
WHERE type = 'CONTROL';

For a comprehensive example demonstrating all the steps in implementing TDE, see Transparent Data Encryption (TDE).

Examples: [!INCLUDEssPDW]

A. Altering the AUTOGROW setting

Set AUTOGROW to ON for database CustomerSales.

ALTER DATABASE CustomerSales  
    SET ( AUTOGROW = ON );

B. Altering the maximum storage for replicated tables

The following example sets the replicated table storage limit to 1 GB for the database CustomerSales. This 1 GB is the storage limit per Compute node.

ALTER DATABASE CustomerSales  
    SET ( REPLICATED_SIZE = 1 GB );

C. Altering the maximum storage for distributed tables

The following example sets the distributed table storage limit to 1000 GB (1 terabyte) for the database CustomerSales. This 1000 GB is the combined storage limit across the appliance for all of the Compute nodes, not the storage limit per Compute node.

ALTER DATABASE CustomerSales  
    SET ( DISTRIBUTED_SIZE = 1000 GB );

D. Altering the maximum storage for the transaction log

The following example updates the database CustomerSales to have a maximum [!INCLUDEssNoVersion] transaction log size of 10 GB for the appliance.

ALTER DATABASE CustomerSales  
    SET ( LOG_SIZE = 10 GB );

::: moniker range=">= aps-pdw-2016-au7 || = sqlallproducts-allversions"

E. Check for current statistics values

The following query returns the current statistics values for all databases. The value 1 means the feature is on, and a 0 means the feature is off.

SELECT NAME,
    is_auto_create_stats_on,
    is_auto_update_stats_on,
    is_auto_update_stats_async_on
FROM sys.databases;

F. Enable auto-create and auto-update stats for a database

Use the following statements to enable create and update statistics automatically and asynchronously for database, CustomerSales. These statements create and update single-column statistics as necessary to create high-quality query plans.

ALTER DATABASE CustomerSales
    SET AUTO_CREATE_STATISTICS ON;
ALTER DATABASE CustomerSales
    SET AUTO_UPDATE_STATISTICS ON; 
ALTER DATABASE CustomerSales
    SET AUTO_UPDATE_STATISTICS_ASYNC ON;

::: moniker-end

See Also

CREATE DATABASE (Parallel Data Warehouse)
DROP DATABASE (Transact-SQL)