ALTER DATABASE SET Options (Transact-SQL)

This topic contains the ALTER DATABASE syntax that is related to setting database options. For other ALTER DATABASE syntax, see ALTER DATABASE (Transact-SQL). Database mirroring and compatibility levels are SET options but are described in separate topics because of their length. For more information, see ALTER DATABASE Database Mirroring (Transact-SQL) and ALTER DATABASE Compatibility Level (Transact-SQL).

Transact-SQL Syntax Conventions

Syntax

ALTER DATABASE database_name 
SET 
{
    { <optionspec> [ ,...n ] [ WITH <termination> ] }
}

<optionspec>::= 
{
    <auto_option> 
  | <change_tracking_option> 
  | <cursor_option> 
  | <database_mirroring_option>
  | <date_correlation_optimization_option>
  | <db_encryption_option>
  | <db_state_option>
  | <db_update_option> 
  | <db_user_access_option>
  | <external_access_option>
  | <parameterization_option>
  | <recovery_option> 
  | <service_broker_option>
  | <snapshot_option>
  | <sql_option> 
}

<auto_option> ::= 

{
    AUTO_CLOSE { ON | OFF } 
  | AUTO_CREATE_STATISTICS { ON | OFF } 
  | AUTO_SHRINK { ON | OFF } 
  | AUTO_UPDATE_STATISTICS { ON | OFF } 
  | AUTO_UPDATE_STATISTICS_ASYNC { ON | OFF }
}

<change_tracking_option> ::=
{
  CHANGE_TRACKING { 
        = ON [ <change_tracking_option_list > ] |
    <change_tracking_option_list> |
        = OFF
  }
}

<change_tracking_option_list> ::=
{
    ( <change_tracking_option> | <change_tracking_option_list> , 
    <change_tracking_option> )
}
  
<change_tracking_option> ::=
{
  AUTO_CLEANUP = { ON | OFF } 
  | CHANGE_RETENTION = { retention_period { DAYS | HOURS | MINUTES } ]
}

<cursor_option> ::= 
{
    CURSOR_CLOSE_ON_COMMIT { ON | OFF } 
  | CURSOR_DEFAULT { LOCAL | GLOBAL } 
}

<database_mirroring_option>ALTER DATABASE Database Mirroring<date_correlation_optimization_option> ::=
{
    DATE_CORRELATION_OPTIMIZATION { ON | OFF }
}

<db_encryption_option> ::=
    ENCRYPTION { ON | OFF }

<db_state_option> ::=
    { ONLINE | OFFLINE | EMERGENCY }

<db_update_option> ::=
    { READ_ONLY | READ_WRITE }

<db_user_access_option> ::=
    { SINGLE_USER | RESTRICTED_USER | MULTI_USER }

<external_access_option> ::=
{
    DB_CHAINING { ON | OFF }

  | TRUSTWORTHY { ON | OFF }
}
<parameterization_option> ::=
{
    PARAMETERIZATION { SIMPLE | FORCED }
}

<recovery_option> ::= 
{
    RECOVERY { FULL | BULK_LOGGED | SIMPLE } 
  | TORN_PAGE_DETECTION { ON | OFF }
  | PAGE_VERIFY { CHECKSUM | TORN_PAGE_DETECTION | NONE }
}

<service_broker_option> ::=
{
    ENABLE_BROKER
  | DISABLE_BROKER
  | NEW_BROKER
  | ERROR_BROKER_CONVERSATIONS
  | HONOR_BROKER_PRIORITY { ON | OFF}
}

<snapshot_option> ::=
{
    ALLOW_SNAPSHOT_ISOLATION { ON | OFF }
  | READ_COMMITTED_SNAPSHOT {ON | OFF }
}
<sql_option> ::= 
{
    ANSI_NULL_DEFAULT { ON | OFF } 
  | ANSI_NULLS { ON | OFF } 
  | ANSI_PADDING { ON | OFF } 
  | ANSI_WARNINGS { ON | OFF } 
  | ARITHABORT { ON | OFF } 
  | COMPATIBILITY_LEVEL = { 80 | 90 | 100 }
  | CONCAT_NULL_YIELDS_NULL { ON | OFF } 
  | NUMERIC_ROUNDABORT { ON | OFF } 
  | QUOTED_IDENTIFIER { ON | OFF } 
  | RECURSIVE_TRIGGERS { ON | OFF } 
}

<termination>::= 
{
    ROLLBACK AFTER integer [ SECONDS ] 
  | ROLLBACK IMMEDIATE 
  | NO_WAIT
}

Arguments

<auto_option>::=

Controls automatic options.

• database_name
  Is the name of the database to be modified.

• AUTO_CLOSE { ON | OFF }

  • ON
    The database is shut down cleanly and its resources are freed after the last user exits.

    The database automatically reopens when a user tries to use the database again. For example, by issuing a USE database_name statement. If the database is shut down cleanly while AUTO_CLOSE is set to ON, the database is not reopened until a user tries to use the database the next time the Database Engine is restarted. 

  • OFF
    The database remains open after the last user exits.

  The AUTO_CLOSE option is useful for desktop databases because it allows for database files to be managed as regular files. They can be moved, copied to make backups, or even e-mailed to other users.

  Note

  In earlier versions of SQL Server, AUTO_CLOSE is a synchronous process that can degrade performance when the database is accessed by an application that repeatedly makes and breaks connections to the Database Engine. Starting in SQL Server 2005, the AUTO_CLOSE process is asynchronous; repeatedly opening and closing the database no longer reduces performance.

  The status of this option can be determined by examining the is_auto_close_on column in the sys.databases catalog view or the IsAutoClose property of the DATABASEPROPERTYEX function.

  Note

  When AUTO_CLOSE is ON, some columns in the sys.databases catalog view and DATABASEPROPERTYEX function will return NULL because the database is unavailable to retrieve the data. To resolve this, execute a USE statement to open the database.

  Note

  Database mirroring requires AUTO_CLOSE OFF.

  When the database is set to AUTOCLOSE = ON, an operation that initiates an automatic database shutdown clears the plan cache for the instance of SQL Server. Clearing the plan cache causes a recompilation of all subsequent execution plans and can cause a sudden, temporary decrease in query performance. In SQL Server 2005 Service Pack 2, for each cleared cachestore in the plan cache, the SQL Server error log contains the following informational message: "SQL Server has encountered %d occurrence(s) of cachestore flush for the '%s' cachestore (part of plan cache) due to some database maintenance or reconfigure operations". This message is logged every five minutes as long as the cache is flushed within that time interval.

• AUTO_CREATE_STATISTICS { ON | OFF }

  • ON
    The query optimizer creates statistics on single columns in query predicates, as necessary, to improve query plans and query performance. These single-column statistics are created when the query optimizer compiles queries. The single-column statistics are created only on columns that are not already the first column of an existing statistics object.

    The default is ON. We recommend that you use the default setting for most databases.

  • OFF
    The query optimizer does not create statistics on single columns in query predicates when it is compiling queries. Setting this option to OFF can cause suboptimal query plans and degraded query performance.

  The status of this option can be determined by examining the is_auto_create_stats_on column in the sys.databases catalog view or the IsAutoCreateStatistics property of the DATABASEPROPERTYEX function.

  For more information, see the section "Using the Database-Wide Statistics Options" in Using Statistics to Improve Query Performance.

• AUTO_SHRINK { ON | OFF }

  • ON
    The database files are candidates for periodic shrinking.

    Both data file and log files can be automatically shrunk. AUTO_SHRINK reduces the size of the transaction log only if the database is set to SIMPLE recovery model or if the log is backed up. When set to OFF, the database files are not automatically shrunk during periodic checks for unused space.

    The AUTO_SHRINK option causes files to be shrunk when more than 25 percent of the file contains unused space. The file is shrunk to a size where 25 percent of the file is unused space, or to the size of the file when it was created, whichever is larger.

    You cannot shrink a read-only database.

  • OFF
    The database files are not automatically shrunk during periodic checks for unused space.

  The status of this option can be determined by examining the is_auto_shrink_on column in the sys.databases catalog view or the IsAutoShrink property of the DATABASEPROPERTYEX function.

• AUTO_UPDATE_STATISTICS { ON | OFF }

  • ON
    Specifies that the query optimizer updates statistics when they are used by a query and when they might be out-of-date. Statistics become out-of-date after insert, update, delete, or merge operations change the data distribution in the table or indexed view. The query optimizer determines when statistics might be out-of-date by counting the number of data modifications since the last statistics update and comparing the number of modifications to a threshold. The threshold is based on the number of rows in the table or indexed view.

    The query optimizer checks for out-of-date statistics before compiling a query and before executing a cached query plan. Before compiling a query, the query optimizer uses the columns, tables, and indexed views in the query predicate to determine which statistics might be out-of-date. Before executing a cached query plan, the Database Engine verifies that the query plan references up-to-date statistics.

    The AUTO_UPDATE_STATISTICS option applies to statistics created for indexes, single-columns in query predicates, and statistics that are created by using the CREATE STATISTICS statement. This option also applies to filtered statistics.

    The default is ON. We recommend that you use the default setting for most databases.

    Use the AUTO_UPDATE_STATISTICS_ASYNC option to specify whether the statistics are updated synchronously or asynchronously.

  • OFF
    Specifies that the query optimizer does not update statistics when they are used by a query and when they might be out-of-date. Setting this option to OFF can cause suboptimal query plans and degraded query performance.

  The status of this option can be determined by examining the is_auto_update_stats_on column in the sys.databases catalog view or the IsAutoUpdateStatistics property of the DATABASEPROPERTYEX function.

  For more information, see the section "Using the Database-Wide Statistics Options" in Using Statistics to Improve Query Performance.

• AUTO_UPDATE_STATISTICS_ASYNC { ON | OFF }

  • ON
    Specifies that statistics updates for the AUTO_UPDATE_STATISTICS option are asynchronous. The query optimizer does not wait for statistics updates to complete before it compiles queries.

    Setting this option to ON has no effect unless AUTO_UPDATE_STATISTICS is set to ON.

    By default, the AUTO_UPDATE_STATISTICS_ASYNC option is set to OFF, and the query optimizer updates statistics synchronously.

  • OFF
    Specifies that statistics updates for the AUTO_UPDATE_STATISTICS option are synchronous. The query optimizer waits for statistcs updates to complete before it compiles queries.

    Setting this option to OFF has no effect unless AUTO_UPDATE_STATISTICS is set to ON.

  The status of this option can be determined by examining the is_auto_update_stats_async_on column in the sys.databases catalog view.

  For more information that describes when to use synchronous or asynchronous statistics updates, see the section "Using the Database-Wide Statistics Options" in Using Statistics to Improve Query Performance.

<change_tracking_option>::=

Controls change tracking options. You can enable change tracking, set options, change options, and disable change tracking. For examples, see the Examples section later in this topic.

• ON
  Enables change tracking for the database. When you enable change tracking, you can also set the AUTO CLEANUP and CHANGE RETENTION options.

• AUTO_CLEANUP = { ON | OFF }

  • ON
    Change tracking information is automatically removed after the specified retention period.

  • OFF
    Change tracking data is not removed from the database.

• CHANGE_RETENTION =retention_period { DAYS | HOURS | MINUTES }
  Specifies the minimum period for keeping change tracking information in the database. Data is removed only when the AUTO_CLEANUP value is ON.

  retention_period is an integer that specifies the numerical component of the retention period.

  The default retention period is 2 days. The minimum retention period is 1 minute.

• OFF
  Disables change tracking for the database. You must disable change tracking on all tables before you can disable change tracking off the database.

<cursor_option>::=

Controls cursor options.

• CURSOR_CLOSE_ON_COMMIT { ON | OFF }

  • ON
    Any cursors open when a transaction is committed or rolled back are closed.

  • OFF
    Cursors remain open when a transaction is committed; rolling back a transaction closes any cursors except those defined as INSENSITIVE or STATIC.

  Connection-level settings that are set by using the SET statement override the default database setting for CURSOR_CLOSE_ON_COMMIT. By default, ODBC and OLE DB clients issue a connection-level SET statement setting CURSOR_CLOSE_ON_COMMIT to OFF for the session when connecting to an instance of SQL Server. For more information, see SET CURSOR_CLOSE_ON_COMMIT (Transact-SQL).

  The status of this option can be determined by examining the is_cursor_close_on_commit_on column in the sys.databases catalog view or the IsCloseCursorsOnCommitEnabled property of the DATABASEPROPERTYEX function.

• CURSOR_DEFAULT { LOCAL | GLOBAL }
  Controls whether cursor scope uses LOCAL or GLOBAL.

  • LOCAL
    When LOCAL is specified and a cursor is not defined as GLOBAL when created, the scope of the cursor is local to the batch, stored procedure, or trigger in which the cursor was created. The cursor name is valid only within this scope. The cursor can be referenced by local cursor variables in the batch, stored procedure, or trigger, or a stored procedure OUTPUT parameter. The cursor is implicitly deallocated when the batch, stored procedure, or trigger ends, unless it was passed back in an OUTPUT parameter. If the cursor is passed back in an OUTPUT parameter, the cursor is deallocated when the last variable that references it is deallocated or goes out of scope.

  • GLOBAL
    When GLOBAL is specified, and a cursor is not defined as LOCAL when created, the scope of the cursor is global to the connection. The cursor name can be referenced in any stored procedure or batch executed by the connection.

  The cursor is implicitly deallocated only at disconnect. For more information, see DECLARE CURSOR (Transact-SQL).

  The status of this option can be determined by examining the is_local_cursor_default column in the sys.databases catalog view or the IsLocalCursorsDefault property of the DATABASEPROPERTYEX function.

<database_mirroring>

For the argument descriptions, see ALTER DATABASE Database Mirroring (Transact-SQL).

<date_correlation_optimization_option> ::=

Controls the date_correlation_optimization option.

• DATE_CORRELATION_OPTIMIZATION { ON | OFF }

  • ON
    SQL Server maintains correlation statistics between any two tables in the database that are linked by a FOREIGN KEY constraint and have datetime columns. For more information, see Optimizing Queries That Access Correlated datetime Columns.

  • OFF
    Correlation statistics are not maintained.

  To set DATE_CORRELATION_OPTIMIZATION to ON, there must be no active connections to the database except for the connection that is executing the ALTER DATABASE statement. Afterwards, multiple connections are supported.

  The current setting of this option can be determined by examining the is_date_correlation_on column in the sys.databases catalog view.

<db_encryption_option>::=

Controls the database encryption state.

• ENCRYPTION {ON | OFF}
  Sets the database to be encrypted (ON) or not encrypted (OFF). For more information about database encryption, see Understanding Transparent Data Encryption (TDE).

When encryption is enabled at the database level all filegroups will be encrypted. Any new filegroups will inherit the encrypted property. If any filegroups in the database are set to READ ONLY, the database encryption operation will fail.

You can see the encryption state of the database by using the sys.dm_database_encryption_keys dynamic management view.

<db_state_option>::=

Controls the state of the database.

• OFFLINE
  The database is closed, shut down cleanly, and marked offline. The database cannot be modified while it is offline.

• ONLINE
  The database is open and available for use.

• EMERGENCY
  The database is marked READ_ONLY, logging is disabled, and access is limited to members of the sysadmin fixed server role. EMERGENCY is primarily used for troubleshooting purposes. For example, a database marked as suspect due to a corrupted log file can be set to the EMERGENCY state. This could enable the system administrator read-only access to the database. Only members of the sysadmin fixed server role can set a database to the EMERGENCY state.

The status of this option can be determined by examining the state and state_desc columns in the sys.databases catalog view or the Status property of the DATABASEPROPERTYEX function. For more information, see Database States.

A database marked as RESTORING cannot be set to OFFLINE, ONLINE, or EMERGENCY. A database may be in the RESTORING state during an active restore operation or when a restore operation of a database or log file fails because of a corrupted backup file. For more information, see Responding to SQL Server Restore Errors Caused by Damaged Backups.

<db_update_option>::=

Controls whether updates are allowed on the database.

• READ_ONLY
  Users can read data from the database but not modify it.

• READ_WRITE
  The database is available for read and write operations.

To change this state, you must have exclusive access to the database. For more information, see the SINGLE_USER clause.

<db_user_access_option> ::=

Controls user access to the database.

• SINGLE_USER
  Specifies that only one user at a time can access the database. If SINGLE_USER is specified and there are other users connected to the database the ALTER DATABASE statement will be blocked until all users disconnect from the specified database. To override this behavior, see the WITH <termination> clause.

  The database remains in SINGLE_USER mode even if the user that set the option logs off. At that point, a different user, but only one, can connect to the database.

  Before you set the database to SINGLE_USER, verify the AUTO_UPDATE_STATISTICS_ASYNC option is set to OFF. When set to ON, the background thread used to update statistics takes a connection against the database, and you will be unable to access the database in single-user mode. To view the status of this option, query the is_auto_update_stats_async_on column in the sys.databases catalog view. If the option is set to ON, perform the following tasks:

  1. Set AUTO_UPDATE_STATISTICS_ASYNC to OFF.

  2. Check for active asynchronous statistics jobs by querying the sys.dm_exec_background_job_queue dynamic management view.

  If there are active jobs, either allow the jobs to complete or manually terminate them by using KILL STATS JOB.

• RESTRICTED_USER
  RESTRICTED_USER allows for only members of the db_owner fixed database role and dbcreator and sysadmin fixed server roles to connect to the database, but does not limit their number. All connections to the database are disconnected in the timeframe specified by the termination clause of the ALTER DATABASE statement. After the database has transitioned to the RESTRICTED_USER state, connection attempts by unqualified users are refused.

• MULTI_USER
  All users that have the appropriate permissions to connect to the database are allowed.

The status of this option can be determined by examining the user_access column in the sys.databases catalog view or the UserAccess property of the DATABASEPROPERTYEX function.

<external_access_option>::=

Controls whether the database can be accessed by external resources, such as objects from another database.

• DB_CHAINING { ON | OFF }

  • ON
    Database can be the source or target of a cross-database ownership chain.

  • OFF
    Database cannot participate in cross-database ownership chaining.

  Important

  The instance of SQL Server will recognize this setting when the cross db ownership chaining server option is 0 (OFF). When cross db ownership chaining is 1 (ON), all user databases can participate in cross-database ownership chains, regardless of the value of this option. This option is set by using sp_configure.

  To set this option, requires CONTROL SERVER permission on the database. The DB_CHAINING option cannot be set on these system databases: master, model, and tempdb.

  The status of this option can be determined by examining the is_db_chaining_on column in the sys.databases catalog view.

  For more information, see Ownership Chains.

• TRUSTWORTHY { ON | OFF }

  • ON
    Database modules (for example, user-defined functions or stored procedures) that use an impersonation context can access resources outside the database.

  • OFF
    Database modules in an impersonation context cannot access resources outside the database.

  TRUSTWORTHY is set to OFF whenever the database is attached.

  By default, all system databases except the msdb database have TRUSTWORTHY set to OFF. The value cannot be changed for the model and tempdb databases. We recommend that you never set the TRUSTWORTHY option to ON for the master database.

  To set this option, requires CONTROL SERVER permission on the database.

  The status of this option can be determined by examining the is_trustworthy_on column in the sys.databases catalog view.

<parameterization_option> ::=

Controls the parameterization option.

• PARAMETERIZATION { SIMPLE | FORCED }

  • SIMPLE
    Queries are parameterized based on the default behavior of the database. For more information, see Simple Parameterization.

  • FORCED
    SQL Server parameterizes all queries in the database. For more information, see Forced Parameterization.

  The current setting of this option can be determined by examining the is_parameterization_forced column in the sys.databases catalog view.

<recovery_option> ::=

Controls database recovery options and disk I/O error checking.

• FULL
  Provides full recovery after media failure by using transaction log backups. If a data file is damaged, media recovery can restore all committed transactions. For more information, see Backup Under the Full Recovery Model.

• BULK_LOGGED
  Provides recovery after media failure by combining the best performance and least amount of log-space use for certain large-scale or bulk operations. For information about what operations are bulk logged, see Operations That Can Be Minimally Logged. Under the BULK_LOGGED recovery model, logging for these operations is minimal. For more information, see Backup Under the Bulk-Logged Recovery Model.

• SIMPLE
  A simple backup strategy that uses minimal log space is provided. Log space can be automatically reused when it is no longer required for server failure recovery. For more information, see Backup Under the Simple Recovery Model.

  Important

  The simple recovery model is easier to manage than the other two models but at the expense of greater data loss exposure if a data file is damaged. All changes since the most recent database or differential database backup are lost and must be manually reentered.

The default recovery model is determined by the recovery model of the model database. For more information about selecting the appropriate recovery model, see Choosing the Recovery Model for a Database.

The status of this option can be determined by examining the recovery_model and recovery_model_desc columns in the sys.databases catalog view or the Recovery property of the DATABASEPROPERTYEX function.

• TORN_PAGE_DETECTION { ON | OFF }

  • ON
    Incomplete pages can be detected by the Database Engine.

  • OFF
    Incomplete pages cannot be detected by the Database Engine.

  Important

  The syntax structure TORN_PAGE_DETECTION ON | OFF will be removed in a future version of SQL Server. Avoid using this syntax structure in new development work, and plan to modify applications that currently use the syntax structure. Use the PAGE_VERIFY option instead.

• PAGE_VERIFY { CHECKSUM | TORN_PAGE_DETECTION | NONE }
  Discovers damaged database pages caused by disk I/O path errors. Disk I/O path errors can be the cause of database corruption problems and are generally caused by power failures or disk hardware failures that occur at the time the page is being written to disk.

  • CHECKSUM
    Calculates a checksum over the contents of the whole page and stores the value in the page header when a page is written to disk. When the page is read from disk, the checksum is recomputed and compared to the checksum value stored in the page header. If the values do not match, error message 824 (indicating a checksum failure) is reported to both the SQL Server error log and the Windows event log. A checksum failure indicates an I/O path problem. To determine the root cause requires investigation of the hardware, firmware drivers, BIOS, filter drivers (such as virus software), and other I/O path components.

  • TORN_PAGE_DETECTION
    Saves a specific 2-bit pattern for each 512-byte sector in the 8-kilobyte (KB) database page and stored in the database page header when the page is written to disk. When the page is read from disk, the torn bits stored in the page header are compared to the actual page sector information. Unmatched values indicate that only part of the page was written to disk. In this situation, error message 824 (indicating a torn page error) is reported to both the SQL Server error log and the Windows event log. Torn pages are typically detected by database recovery if it is truly an incomplete write of a page. However, other I/O path failures can cause a torn page at any time.

  • NONE
    Database page writes will not generate a CHECKSUM or TORN_PAGE_DETECTION value. SQL Server will not verify a checksum or torn page during a read even if a CHECKSUM or TORN_PAGE_DETECTION value is present in the page header.

  Consider the following important points when you use the PAGE_VERIFY option:

  • In SQL Server 2005 and SQL Server 2008, the default is CHECKSUM. In SQL Server 2000, TORN_PAGE_DETECTION is the default.

  • When a user or system database is upgraded to SQL Server 2005 or SQL Server 2008, the PAGE_VERIFY value (NONE or TORN_PAGE_DETECTION) is retained. We recommend that you use CHECKSUM. 

    Note

    In earlier versions of SQL Server, the PAGE_VERIFY database option is set to NONE for the tempdb database and cannot be modified. In SQL Server 2008, the default value for the tempdb database is CHECKSUM for new installations of SQL Server. When upgrading an installation SQL Server, the default value remains NONE. The option can be modified. We recommend that you use CHECKSUM for the tempdb database.

  • TORN_PAGE_DETECTION may use fewer resources but provides a minimal subset of the CHECKSUM protection.

  • PAGE_VERIFY can be set without taking the database offline, locking the database, or otherwise impeding concurrency on that database.

  • CHECKSUM is mutually exclusive to TORN_PAGE_DETECTION. Both options cannot be enabled at the same time.

  When a torn page or checksum failure is detected, you can recover by restoring the data or potentially rebuilding the index if the failure is limited only to index pages. If you encounter a checksum failure, to determine the type of database page or pages affected, run DBCC CHECKDB. For more information about restore options, see RESTORE Arguments (Transact-SQL). Although restoring the data will resolve the data corruption problem, the root cause, for example, disk hardware failure, should be diagnosed and corrected as soon as possible to prevent continuing errors.

  SQL Server will retry any read that fails with a checksum, torn page, or other I/O error four times. If the read is successful in any one of the retry attempts, a message will be written to the error log and the command that triggered the read will continue. If the retry attempts fail, the command will fail with error message 824.

  For more information about checksum, torn page, read-retry, error messages 823 and 824, and other SQL Server I/O auditing features, see this Microsoft Web site.

  The current setting of this option can be determined by examining the page_verify_option column in the sys.databases catalog view or the IsTornPageDetectionEnabled property of the DATABASEPROPERTYEX function.

<service_broker_option>::=

Controls the following Service Broker options: enables or disables message delivery, sets a new Service Broker identifier, or sets conversation priorities to ON or OFF. For more information about message deliver and Service Broker identifiers, see Managing Service Broker Identities. For more information about conversation priority levels, see Conversation Priorities. For examples that show how to use the HONOR_BROKER_PRIORITY option, see Managing Conversation Priorities.

• ENABLE_BROKER
  Specifies that Service Broker is enabled for the specified database. Message delivery is started, and the is_broker_enabled flag is set to true in the sys.databases catalog view. The database retains the existing Service Broker identifier.

  Note

  ENABLE_BROKER requires an exclusive database lock. If other sessions have locked resources in the database, ENABLE_BROKER will wait until the other sessions release their locks. To enable Service Broker in a user database, ensure that no other sessions are using the database before you run the ALTER DATABASE SET ENABLE_BROKER statement, such as by putting the database in single user mode. To enable Service Broker in the msdb database, first stop SQL Server Agent so that Service Broker can obtain the necessary lock.

• DISABLE_BROKER
  Specifies that Service Broker is disabled for the specified database. Message delivery is stopped, and the is_broker_enabled flag is set to false in the sys.databases catalog view. The database retains the existing Service Broker identifier.

• NEW_BROKER
  Specifies that the database should receive a new broker identifier. Because the database is considered to be a new service broker, all existing conversations in the database are immediately removed without producing end dialog messages. Any route that references the old Service Broker identifier must be re-created with the new identifier.

• ERROR_BROKER_CONVERSATIONS
  Specifies that Service Broker message delivery is enabled. This preserves the existing Service Broker identifier for the database. Service Broker ends all conversations in the database with an error. This enables applications to perform regular cleanup for existing conversations.

• HONOR_BROKER_PRIORITY {ON | OFF}

  • ON
    Send operations take into consideration the priority levels that are assigned to conversations. Messages from conversations that have high priority levels are sent before messages from conversations that are assigned low priority levels.

  • OFF
    Send operations run as if all conversations have the default priority level.

  Changes to the HONOR_BROKER_PRIORITY option take effect immediately for new dialogs or dialogs that have no messages waiting to be sent. Dialogs that have messages waiting to be sent when ALTER DATABASE is run will not pick up the new setting until some of the messages for the dialog have been sent. The amount of time before all dialogs start using the new setting can vary considerably.

  The current setting of this property is reported in the is_broker_priority_honored column in the sys.databases catalog view.

<snapshot_option>::=

Determines the transaction isolation level.

• ALLOW_SNAPSHOT_ISOLATION { ON | OFF }

  • ON
    Enables Snapshot option at the database level. When it is enabled, DML statements start generating row versions even when no transaction uses Snapshot Isolation. Once this option is enabled, transactions can specify the SNAPSHOT transaction isolation level. When a transaction runs at the SNAPSHOT isolation level, all statements see a snapshot of data as it exists at the start of the transaction. If a transaction running at the SNAPSHOT isolation level accesses data in multiple databases, either ALLOW_SNAPSHOT_ISOLATION must be set to ON in all the databases, or each statement in the transaction must use locking hints on any reference in a FROM clause to a table in a database where ALLOW_SNAPSHOT_ISOLATION is OFF.

  • OFF
    Turns off Snapshot option at the database level. Transactions cannot specify the SNAPSHOT transaction isolation level.

  When you set ALLOW_SNAPSHOT_ISOLATION to a new state (from ON to OFF, or from OFF to ON), ALTER DATABASE does not return control to the caller until all existing transactions in the database are committed. If the database is already in the state specified in the ALTER DATABASE statement, control is returned to the caller immediately. If the ALTER DATABASE statement does not return quickly, use sys.dm_tran_active_snapshot_database_transactions to determine whether there are long-running transactions. If the ALTER DATABASE statement is canceled, the database remains in the state it was in when ALTER DATABASE was started. The sys.databases catalog view indicates the state of snapshot-isolation transactions in the database. If snapshot_isolation_state_desc = IN_TRANSITION_TO_ON, ALTER DATABASE ALLOW_SNAPSHOT_ISOLATION OFF will pause six seconds and retry the operation.

  You cannot change the state of ALLOW_SNAPSHOT_ISOLATION if the database is OFFLINE.

  If you set ALLOW_SNAPSHOT_ISOLATION in a READ_ONLY database, the setting will be retained if the database is later set to READ_WRITE.

  You can change the ALLOW_SNAPSHOT_ISOLATION settings for the master, model, msdb, and tempdb databases. If you change the setting for tempdb, the setting is retained every time the instance of the Database Engine is stopped and restarted. If you change the setting for model, that setting becomes the default for any new databases that are created, except for tempdb.

  The option is ON, by default, for the master and msdb databases.

  The current setting of this option can be determined by examining the snapshot_isolation_state column in the sys.databases catalog view.

• READ_COMMITTED_SNAPSHOT { ON | OFF }

  • ON
    Enables Read-Committed Snapshot option at the database level. When it is enabled, DML statements start generating row versions even when no transaction uses Snapshot Isolation. Once this option is enabled, the transactions specifying the read committed isolation level use row versioning instead of locking. When a transaction runs at the read committed isolation level, all statements see a snapshot of data as it exists at the start of the statement.

  • OFF
    Turns off Read-Committed Snapshot option at the database level. Transactions specifying the READ COMMITTED isolation level use locking.

  To set READ_COMMITTED_SNAPSHOT ON or OFF, there must be no active connections to the database except for the connection executing the ALTER DATABASE command. However, the database does not have to be in single-user mode. You cannot change the state of this option when the database is OFFLINE.

  If you set READ_COMMITTED_SNAPSHOT in a READ_ONLY database, the setting will be retained when the database is later set to READ_WRITE.

  READ_COMMITTED_SNAPSHOT cannot be turned ON for the master, tempdb, or msdb system databases. If you change the setting for model, that setting becomes the default for any new databases created, except for tempdb.

  The current setting of this option can be determined by examining the is_read_committed_snapshot_on column in the sys.databases catalog view.

<sql_option>::=

Controls the ANSI compliance options at the database level.

• ANSI_NULL_DEFAULT { ON | OFF }
  Determines the default value, NULL or NOT NULL, of a column, alias data type, or CLR user-defined type for which the nullability is not explicitly defined in CREATE TABLE or ALTER TABLE statements. Columns that are defined with constraints follow constraint rules regardless of this setting.

  • ON
    The default value is NULL.

  • OFF
    The default value is NOT NULL.

  Connection-level settings that are set by using the SET statement override the default database-level setting for ANSI_NULL_DEFAULT. By default, ODBC and OLE DB clients issue a connection-level SET statement setting ANSI_NULL_DEFAULT to ON for the session when connecting to an instance of SQL Server. For more information, see SET ANSI_NULL_DFLT_ON (Transact-SQL).

  For ANSI compatibility, setting the database option ANSI_NULL_DEFAULT to ON changes the database default to NULL.

  The status of this option can be determined by examining the is_ansi_null_default_on column in the sys.databases catalog view or the IsAnsiNullDefault property of the DATABASEPROPERTYEX function.

• ANSI_NULLS { ON | OFF }

  • ON
    All comparisons to a null value evaluate to UNKNOWN.

  • OFF
    Comparisons of non-UNICODE values to a null value evaluate to TRUE if both values are NULL.

  Important

  In a future version of SQL Server, ANSI_NULLS will always be ON and any applications that explicitly set the option to OFF will produce an error. Avoid using this feature in new development work, and plan to modify applications that currently use this feature.

  Connection-level settings that are set by using the SET statement override the default database setting for ANSI_NULLS. By default, ODBC and OLE DB clients issue a connection-level SET statement setting ANSI_NULLS to ON for the session when connecting to an instance of SQL Server. For more information, see SET ANSI_NULLS (Transact-SQL).

  SET ANSI_NULLS also must be set to ON when you create or make changes to indexes on computed columns or indexed views.

  The status of this option can be determined by examining the is_ansi_nulls_on column in the sys.databases catalog view or the IsAnsiNullsEnabled property of the DATABASEPROPERTYEX function.

• ANSI_PADDING { ON | OFF }

  • ON
    Strings are padded to the same length before conversion or inserting to a varchar or nvarchar data type.

    Trailing blanks in character values inserted into varchar or nvarchar columns and trailing zeros in binary values inserted into varbinary columns are not trimmed. Values are not padded to the length of the column.

  • OFF
    Trailing blanks for varchar or nvarchar and zeros for varbinary are trimmed.

  When OFF is specified, this setting affects only the definition of new columns.

  Important

  In a future version of SQL Server, ANSI_PADDING will always be ON and any applications that explicitly set the option to OFF will produce an error. Avoid using this feature in new development work, and plan to modify applications that currently use this feature.

  char(n) and binary(n) columns that allow for nulls are padded to the length of the column when ANSI_PADDING is set to ON, but trailing blanks and zeros are trimmed when ANSI_PADDING is OFF. char(n) and binary(n) columns that do not allow nulls are always padded to the length of the column.

  Connection-level settings that are set by using the SET statement override the default database-level setting for ANSI_PADDING. By default, ODBC and OLE DB clients issue a connection-level SET statement setting ANSI_PADDING to ON for the session when connecting to an instance of SQL Server. For more information, see SET ANSI_PADDING (Transact-SQL).

  Important

  We recommend that ANSI_PADDING always be set to ON. ANSI_PADDING must be ON when you create or manipulate indexes on computed columns or indexed views.

  The status of this option can be determined by examining the is_ansi_padding_on column in the sys.databases catalog view or the IsAnsiPaddingEnabled property of the DATABASEPROPERTYEX function.

• ANSI_WARNINGS { ON | OFF }

  • ON
    Errors or warnings are issued when conditions such as divide-by-zero occur or null values appear in aggregate functions.

  • OFF
    No warnings are raised and null values are returned when conditions such as divide-by-zero occur.

  SET ANSI_WARNINGS must be set to ON when you create or make changes to indexes on computed columns or indexed views.

  Connection-level settings that are set by using the SET statement override the default database setting for ANSI_WARNINGS. By default, ODBC and OLE DB clients issue a connection-level SET statement setting ANSI_WARNINGS to ON for the session when connecting to an instance of SQL Server. For more information, see SET ANSI_WARNINGS (Transact-SQL).

  The status of this option can be determined by examining the is_ansi_warnings_on column in the sys.databases catalog view or the IsAnsiWarningsEnabled property of the DATABASEPROPERTYEX function.

• ARITHABORT { ON | OFF }

  • ON
    A query is ended when an overflow or divide-by-zero error occurs during query execution.

  • OFF
    A warning message is displayed when one of these errors occurs, but the query, batch, or transaction continues to process as if no error occurred.

  SET ARITHABORT must be set to ON when you create or make changes to indexes on computed columns or indexed views.

  The status of this option can be determined by examining the is_arithabort_on column in the sys.databases catalog view or the IsArithmeticAbortEnabled property of the DATABASEPROPERTYEX function.

• COMPATIBILITY_LEVEL { 80 | 90 | 100 }
  For more information, see ALTER DATABASE Compatibility Level (Transact-SQL).

• CONCAT_NULL_YIELDS_NULL { ON | OFF }

  • ON
    The result of a concatenation operation is NULL when either operand is NULL. For example, concatenating the character string "This is" and NULL causes the value NULL, instead of the value "This is".

  • OFF
    The null value is treated as an empty character string.

  CONCAT_NULL_YIELDS_NULL must be set to ON when you create or make changes to indexes on computed columns or indexed views.

  Important

  In a future version of SQL Server, CONCAT_NULL_YIELDS_NULL will always be ON and any applications that explicitly set the option to OFF will produce an error. Avoid using this feature in new development work, and plan to modify applications that currently use this feature.

  Connection-level settings that are set by using the SET statement override the default database setting for CONCAT_NULL_YIELDS_NULL. By default, ODBC and OLE DB clients issue a connection-level SET statement setting CONCAT_NULL_YIELDS_NULL to ON for the session when connecting to an instance of SQL Server. For more information, see SET CONCAT_NULL_YIELDS_NULL (Transact-SQL).

  The status of this option can be determined by examining the is_concat_null_yields_null_on column in the sys.databases catalog view or the IsNullConcat property of the DATABASEPROPERTYEX function.

• QUOTED_IDENTIFIER { ON | OFF }

  • ON
    Double quotation marks can be used to enclose delimited identifiers.

    All strings delimited by double quotation marks are interpreted as object identifiers. Quoted identifiers do not have to follow the Transact-SQL rules for identifiers. They can be keywords and can include characters not generally allowed in Transact-SQL identifiers. If a single quotation mark (') is part of the literal string, it can be represented by double quotation marks (").

  • OFF
    Identifiers cannot be in quotation marks and must follow all Transact-SQL rules for identifiers. Literals can be delimited by either single or double quotation marks.

  SQL Server also allows for identifiers to be delimited by square brackets ([ ]). Bracketed identifiers can always be used, regardless of the setting of QUOTED_IDENTIFIER. For more information, see Delimited Identifiers (Database Engine).

  When a table is created, the QUOTED IDENTIFIER option is always stored as ON in the metadata of the table, even if the option is set to OFF when the table is created.

  Connection-level settings that are set by using the SET statement override the default database setting for QUOTED_IDENTIFIER. By default, ODBC and OLE DB clients issue a connection-level SET statement setting QUOTED_IDENTIFIER to ON when connecting to an instance of SQL Server. For more information, see SET QUOTED_IDENTIFIER (Transact-SQL).

  The status of this option can be determined by examining the is_quoted_identifier_on column in the sys.databases catalog view or the IsQuotedIdentifiersEnabled property of the DATABASEPROPERTYEX function.

• NUMERIC_ROUNDABORT { ON | OFF }

  • ON
    An error is generated when loss of precision occurs in an expression.

  • OFF
    Losses of precision do not generate error messages and the result is rounded to the precision of the column or variable storing the result.

  NUMERIC_ROUNDABORT must be set to OFF when you create or make changes to indexes on computed columns or indexed views.

  The status of this option can be determined by examining the is_numeric_roundabort_on column in the sys.databases catalog view or the IsNumericRoundAbortEnabled property of the DATABASEPROPERTYEX function.

• RECURSIVE_TRIGGERS { ON | OFF }

  • ON
    Recursive firing of AFTER triggers is allowed.

  • OFF
    Only direct recursive firing of AFTER triggers is not allowed. To also disable indirect recursion of AFTER triggers, set the nested triggers server option to 0 by using sp_configure.

  Note

  Only direct recursion is prevented when RECURSIVE_TRIGGERS is set to OFF. To disable indirect recursion, you must also set the nested triggers server option to 0.

  The status of this option can be determined by examining the is_recursive_triggers_on column in the sys.databases catalog view or the IsRecursiveTriggersEnabled property of the DATABASEPROPERTYEX function.

WITH <termination>::=

Specifies when to roll back incomplete transactions when the database is transitioned from one state to another. If the termination clause is omitted, the ALTER DATABASE statement waits indefinitely if there is any lock on the database. Only one termination clause can be specified, and it follows the SET clauses.

Note

Not all database options use the WITH <termination> clause. For more information, see the table under "Setting Options" in the Remarks section.

• ROLLBACK AFTER integer [SECONDS] | ROLLBACK IMMEDIATE
  Specifies whether to roll back after the specified number of seconds or immediately.

• NO_WAIT
  Specifies that if the requested database state or option change cannot complete immediately without waiting for transactions to commit or roll back on their own, the request will fail.

Remarks

Setting Options

To retrieve current settings for database options, use the sys.databases catalog view or DATABASEPROPERTYEX. For a list of default values assigned to the database when it is first created, see Setting Database Options.

After you set a database option, the modification takes effect immediately.

To change the default values for any one of the database options for all newly created databases, change the appropriate database option in the model database.

Not all database options use the WITH <termination> clause or can be specified in combination with other options. The following table lists these options and their option and termination status.

Options category	Can be specified with other options	Can use the WITH <termination> clause
<db_state_option>	Yes	Yes
<db_user_access_option>	Yes	Yes
<db_update_option>	Yes	Yes
<external_access_option>	Yes	No
<cursor_option>	Yes	No
<auto_option>	Yes	No
<sql_option>	Yes	No
<recovery_option>	Yes	No
<database_mirroring_option>	No	No
ALLOW_SNAPSHOT_ISOLATION	No	No
READ_COMMITTED_SNAPSHOT	No	Yes
<service_broker_option>	Yes	No
DATE_CORRELATION_OPTIMIZATION	Yes	Yes
<parameterization_option>	Yes	Yes
<change_tracking_option>	Yes	Yes
<db_encryption>	Yes	No

The plan cache for the instance of SQL Server is cleared by setting one of the following options:

OFFLINE	READ_WRITE
ONLINE	MODIFY FILEGROUP DEFAULT
MODIFY_NAME	MODIFY FILEGROUP READ_WRITE
COLLATE	MODIFY FILEGROUP READ_ONLY
READ_ONLY

Clearing the plan cache causes a recompilation of all subsequent execution plans and can cause a sudden, temporary decrease in query performance. For each cleared cachestore in the plan cache, the SQL Server error log contains the following informational message: "SQL Server has encountered %d occurrence(s) of cachestore flush for the '%s' cachestore (part of plan cache) due to some database maintenance or reconfigure operations". This message is logged every five minutes as long as the cache is flushed within that time interval. 

Examples

A. Setting options on a database

The following example sets the recovery model and data page verification options for the AdventureWorks sample database.

USE master;
GO
ALTER DATABASE AdventureWorks 
SET RECOVERY FULL, PAGE_VERIFY CHECKSUM;
GO

B. Setting the database to READ_ONLY

Changing the state of a database or filegroup to READ_ONLY or READ_WRITE requires exclusive access to the database. The following example sets the database to SINGLE_USER mode to obtain exclusive access. The example then sets the state of the AdventureWorks database to READ_ONLY and returns access to the database to all users.

Note

This example uses the termination option WITH ROLLBACK IMMEDIATE in the first ALTER DATABASE statement. All incomplete transactions will be rolled back and any other connections to the AdventureWorks sample database will be immediately disconnected.

USE master;
GO
ALTER DATABASE AdventureWorks
SET SINGLE_USER
WITH ROLLBACK IMMEDIATE;
GO
ALTER DATABASE AdventureWorks
SET READ_ONLY;
GO
ALTER DATABASE AdventureWorks
SET MULTI_USER;
GO

C. Enabling snapshot isolation on a database

The following example enables the snapshot isolation framework option for the AdventureWorks database.

USE AdventureWorks;
GO
-- Check the state of the snapshot_isolation_framework
-- in the database.
SELECT name, snapshot_isolation_state,
     snapshot_isolation_state_desc AS description
FROM sys.databases
WHERE name = N'AdventureWorks';
GO
USE master;
GO
ALTER DATABASE AdventureWorks
    SET ALLOW_SNAPSHOT_ISOLATION ON;
GO
-- Check again.
SELECT name, snapshot_isolation_state,
     snapshot_isolation_state_desc AS description
FROM sys.databases
WHERE name = N'AdventureWorks';
GO

The result set shows that the snapshot isolation framework is enabled.

name            snapshot_isolation_state  description
--------------- ------------------------  -----------
AdventureWorks  1                         ON

D. Enabling, modifying, and disabling change tracking

The following example enables change tracking for the AdventureWorks database and sets the retention period to 4 days.

ALTER DATABASE AdventureWorks
SET CHANGE_TRACKING = ON
(AUTO_CLEANUP = ON, CHANGE_RETENTION = 2 DAYS);

The following example shows how to change the retention period to 3 days.

ALTER DATABASE AdventureWorks
SET CHANGE_TRACKING (CHANGE_RETENTION = 3 DAYS);

The following example shows how to disable change tracking for the AdventureWorks database.

ALTER DATABASE AdventureWorks
SET CHANGE_TRACKING = OFF;

Change History for Document

Updated content
Revised the descriptions for AUTO_CREATE_STATISTICS, AUTO_UPDATE_STATISTICS, and AUTO_UPDATE_STATISTICS_ASYNC to improve accuracy.

See Also

Reference

CREATE DATABASE (Transact-SQL)

DATABASEPROPERTYEX (Transact-SQL)

DROP DATABASE (Transact-SQL)

SET TRANSACTION ISOLATION LEVEL (Transact-SQL)

sp_configure (Transact-SQL)

sys.databases (Transact-SQL)

sys.data_spaces (Transact-SQL)

Concepts

Using Statistics to Improve Query Performance

Configuring and Managing Change Tracking

Enabling Row Versioning-Based Isolation Levels