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# DBCC TRACEON - Trace Flags (Transact-SQL)
[!INCLUDE[tsql-appliesto-ss2012-xxxx-xxxx-xxx-md](../../includes/tsql-appliesto-ss2012-xxxx-xxxx-xxx-md.md)]

Trace flags are used to temporarily set specific server characteristics or to switch off a particular behavior. For example, if trace flag 3205 is set when an instance of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] starts, hardware compression for tape drivers is disabled. Trace flags are frequently used to diagnose performance issues or to debug stored procedures or complex computer systems.
  
The following table lists and describes the trace flags that are available in [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)].
 
> [!NOTE]
> Some trace flags were introduced in specific [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] versions. For more information on the applicable version, see the Microsoft Support article associated with a specific trace flag.

> [!IMPORTANT]
> Trace flag behavior may not be supported in future releases of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)]. 

  
|Trace flag|Description|  
|---|---|
|**139**| Forces correct conversion semantics in the scope of DBCC check commands like [DBCC CHECKDB](../../t-sql/database-console-commands/dbcc-checkdb-transact-sql.md), [DBCC CHECKTABLE](../../t-sql/database-console-commands/dbcc-checktable-transact-sql.md) and [DBCC CHECKCONSTRAINTS](../../t-sql/database-console-commands/dbcc-checkconstraints-transact-sql.md), when analyzing the improved precision and conversion logic introduced with compatibility level 130 for specific data types, on a database that has a lower compatibility level. For more information, see this [Microsoft Support article](http://support.microsoft.com/help/4010261).<br /><br />**Note:** This trace flag applies to [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] RTM CU3, [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1 and higher builds.<br /><br />**WARNING:** Trace flag 139 is not meant to be enabled continuously in a production environment, and should be used for the sole purpose of performing database validation checks described in this [Microsoft Support article](http://support.microsoft.com/help/4010261). It should be immediately disabled after validation checks are completed.<br /><br />**Scope**: global only|
|**174**|Increases the [!INCLUDE[ssDEnoversion](../../includes/ssdenoversion-md.md)] plan cache bucket count from 40,009 to 160,001 on 64-bit systems. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3026083).<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Scope**: global only|
|**176**|Enables a fix to address errors when rebuilding partitions online for tables that contain a computed partitioning column. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3213683).<br /><br />**Scope**: global or session|
|**205**|Reports to the error log when a statistics-dependent stored procedure is being recompiled as a result of auto-update statistics. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/195565).<br /><br />**Scope**: global only|
|**260**|Prints versioning information about extended stored procedure dynamic-link libraries (DLLs). For more information about **GetXpVersion()**, see [Creating Extended Stored Procedures](../../relational-databases/extended-stored-procedures-programming/creating-extended-stored-procedures.md).<br /><br />**Scope:** global or session|
|**272**|Disables identity pre-allocation to avoid gaps in the values of an identity column in cases where the server restarts unexpectedly or fails over to a secondary server. Note that identity caching is used to improve INSERT performance on tables with identity columns.<br /><br />**Note:** Starting with [!INCLUDE[ssSQL17](../../includes/sssql17-md.md)], to accomplish this at the database level, see the IDENTITY_CACHE option in [ALTER DATABASE SCOPED CONFIGURATION &#40;Transact-SQL&#41;](../../t-sql/statements/alter-database-scoped-configuration-transact-sql.md).<br /><br />**Scope**: global only|
|**610**|Controls minimally logged inserts into indexed tables. This trace flag is not required starting SQL Server 2016 as minimal logging is turned on by default for indexed tables. In SQL Server 2016, when the bulk load operation causes a new page to be allocated, all of the rows sequentially filling that new page are minimally logged if all the other pre-requisites for minimal logging are met. Rows inserted into existing pages (no new page allocation) to maintain index order are still fully logged, as are rows that are moved as a result of page splits during the load. It is also important to have ALLOW_PAGE_LOCKS turned ON for indexes (which is ON by default) for minimal logging operation to work as page locks are acquired during allocation and thereby only page or extent allocations are logged.For more information, see [Data Loading Performance Guide](https://msdn.microsoft.com/library/dd425070.aspx).<br /><br />**Scope**: global or session|
|**634**|Disables the background columnstore compression task. [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] periodically runs the Tuple Mover background task that compresses columnstore index rowgroups with uncompressed data, one such rowgroup at a time.<br /><br />Columnstore compression improves query performance but also consumes system resources. You can control the timing of columnstore compression manually, by disabling the background compression task with trace flag 634, and then explicitly invoking ALTER INDEX...REORGANIZE or ALTER INDEX...REBUILD at the time of your choice.<br /><br />**Scope:** global only|
|**652**|Disables page pre-fetching scans. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/920093).<br /><br />**Scope**: global or session|
|**661**|Disables the ghost record removal process. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/920093).<br /><br />**Scope**: global only|
|**692**|Disables fast inserts while bulk loading data into heap or clustered index. Starting [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)], fast inserts is enabled by default leveraging minimal logging when database is in simple or bulk logged recovery model to optimize insert performance for records inserted into new pages. With fast inserts, each bulk load batch acquires new extent(s) bypassing the allocation lookup for existing extent with available free space to optimize insert performance.<br /><br /> With fast inserts, bulk loads with small batch sizes can lead to increased unused space consumed by objects hence it is recommended to use large batchsize for each batch to fill the extent completely. If increasing batchsize is not feasible, this traceflag can help reduce unused space reserved at the expense of performance. <br /><br />**Note:** This trace flag applies to [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] RTM and higher builds.<br /><br />**Scope**: global or session|
|**715**|Enables table lock for bulk load operations into a heap with no non-clustered indexes. When this trace flag is enabled, bulk load operations acquire bulk update (BU) locks when bulk copying data into a table. Bulk update (BU) locks allow multiple threads to bulk load data concurrently into the same table, while preventing other processes that are not bulk loading data from accessing the table.<br /><br />The behavior is similar to when the user explicitly specifies TABLOCK hint while performing bulk load, or when the sp_tableoption table lock on bulk load is enabled for a given table. However, when this trace flag is enabled, this behavior becomes default without any query or database changes.<br /><br />**Scope:** global or session|
|**834**|Uses Microsoft Windows large-page allocations for the buffer pool. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3210239).<br /><br />**Note:** If you are using the Columnstore Index feature of [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] to [!INCLUDE[ssCurrent](../../includes/sscurrent-md.md)], we do not recommend turning on trace flag 834.<br /><br />**Scope**: global only|
|**845**|Enables locked pages on Standard SKUs of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)], when the service account for [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] has the Lock Pages in Memory privilege enabled. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/970070) and the documentation page on [Server Memory Server Configuration Options](../../database-engine/configure-windows/server-memory-server-configuration-options.md#lock-pages-in-memory-lpim).<br /><br />**Note:** Starting with [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] this behavior is enabled by default for Standard SKUs, and trace flag 845 must not be used.<br /><br />**Scope**: global only|
|**902**|Bypasses execution of database upgrade script when installing a Cumulative Update or Service Pack. If you encounter an error during script upgrade mode, it is recommended to contact Microsoft SQL Customer Service and Support (CSS) for further guidance. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2163980).<br /><br />**WARNING:** This trace flag is meant for troubleshooting of failed updates during script upgrade mode, and it is not supported to run it continuously in a production environment. Database upgrade scripts needs to execute successfully for a complete install of Cumulative Updates and Service Packs. Not doing so can cause unexpected issues with your [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] instance.<br /><br />**Scope**: global only|
|**1117**|When a file in the filegroup meets the autogrow threshold, all files in the filegroup grow.<br /><br />**Note:** Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] this behavior is controlled by the AUTOGROW_SINGLE_FILE and AUTOGROW_ALL_FILES option of ALTER DATABASE, and trace flag 1117 has no effect. For more information, see [ALTER DATABASE File and Filegroup Options &#40;Transact-SQL&#41;](../../t-sql/statements/alter-database-transact-sql-file-and-filegroup-options.md).<br /><br />**Scope:** global only|
|**1118**|Removes most single page allocations on the server, reducing contention on the SGAM page. When a new object is created, by default, the first eight pages are allocated from different extents (mixed extents). Afterwards, when more pages are needed, those are allocated from that same extent (uniform extent). The SGAM page is used to track these mixed extents, so can quickly become a bottleneck when numerous mixed page allocations are occurring. This trace flag allocates all eight pages from the same extent when creating new objects, minimizing the need to scan the SGAM page. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/328551).<br /><br />**Note:** Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] this behavior is controlled by the SET MIXED_PAGE_ALLOCATION option of ALTER DATABASE, and trace flag 1118 has no effect. For more information, see [ALTER DATABASE SET Options &#40;Transact-SQL&#41;](../../t-sql/statements/alter-database-transact-sql-set-options.md).<br /><br />**Scope:** global only|  
|**1204**|Returns the resources and types of locks participating in a deadlock and also the current command affected. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/832524).<br /><br />**Scope:** global only|  
|**1211**|Disables lock escalation based on memory pressure, or based on number of locks. The [!INCLUDE[ssDEnoversion](../../includes/ssdenoversion-md.md)] will not escalate row or page locks to table locks.<br /><br />Using this trace flag can generate excessive numbers of locks. This can slow the performance of the [!INCLUDE[ssDE](../../includes/ssde-md.md)], or cause 1204 errors (unable to allocate lock resource) because of insufficient memory.<br /><br />If both trace flag 1211 and 1224 are set, 1211 takes precedence over 1224. However, because trace flag 1211 prevents escalation in every case, even under memory pressure, we recommend that you use 1224. This helps avoid "out-of-locks" errors when many locks are being used.<br /><br />**Scope**: global or session|  
|**1222**|Returns the resources and types of locks that are participating in a deadlock and also the current command affected, in an XML format that does not comply with any XSD schema.<br /><br />**Scope**: global only|  
|**1224**|Disables lock escalation based on the number of locks. However, memory pressure can still activate lock escalation. The [!INCLUDE[ssDE](../../includes/ssde-md.md)] escalates row or page locks to table (or partition) locks if the amount of memory used by lock objects exceeds one of the following conditions:<br /><br />-   Forty percent of the memory that is used by [!INCLUDE[ssDE](../../includes/ssde-md.md)]. This is applicable only when the **locks** parameter of sp_configure is set to 0.<br />-   Forty percent of the lock memory that is configured by using the **locks** parameter of sp_configure. For more information, see [Server Configuration Options &#40;SQL Server&#41;](../../database-engine/configure-windows/server-configuration-options-sql-server.md).<br /><br />If both trace flag 1211 and 1224 are set, 1211 takes precedence over 1224. However, because trace flag 1211 prevents escalation in every case, even under memory pressure, we recommend that you use 1224. This helps avoid "out-of-locks" errors when many locks are being used.<br /><br />**Note:** Lock escalation to the table-level or HoBT-level granularity can also be controlled by using the LOCK_ESCALATION option of the [ALTER TABLE](../../t-sql/statements/alter-table-transact-sql.md) statement.<br /><br />**Scope:** global or session|
|**1236**|Enables database lock partitioning. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2926217).<br /><br />**Note:** Starting with [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] SP3 and [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] SP1 this behavior is controlled by the engine and trace flag 1236 has no effect.<br /><br />**Scope**: global only|
|**1237**|Allows the ALTER PARTITION FUNCTION statement to honor the current user-defined session deadlock priority instead of being the likely deadlock victim by default. For more information, see this [Microsoft Support article](http://support.microsoft.com/help/4025261).<br /><br />**Note:** Starting with [!INCLUDE[ssSQLv14](../../includes/sssqlv14-md.md)] and database [compatibility level](../../t-sql/statements/alter-database-transact-sql-compatibility-level.md) 140 this is the default behavior and trace flag 1237 has no effect.<br /><br />**Scope**: global or session or query|
|**1260**|Disable scheduler monitor dumps.<br /><br />**Scope**: global only|   
|**1448**|Enables the replication log reader to move forward even if the async secondaries have not acknowledged the reception of a change. Even with this trace flag enabled the log reader always waits for the sync secondaries. The log reader will not go beyond the min ack of the sync secondaries. This trace flag applies to the instance of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)], not just an availability group, an availability database, or a log reader instance. Takes effect immediately without a restart. This trace flag can be activated ahead of time or when an async secondary fails. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/937041).<br /><br />**Scope**: global only|   
|**1462**|Disables log stream compression for asynchronous availability groups. This feature is enabled by default on asynchronous availability groups in order to optimize network bandwidth. For more information, see [Tune compression for availability group](../../database-engine/availability-groups/windows/tune-compression-for-availability-group.md).<br /><br />**Scope**: global only| 
|**1800**|Enables [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] optimization when disks of different sector sizes are used for primary and secondary replica log files, in [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] Always On and Log Shipping environments. This trace flag is only required to be enabled on SQL Server instances with transaction log file residing on disk with sector size of 512 bytes. It is **not** required to be enabled on disk with 4k sector sizes. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3009974).<br /><br />**Scope:** global only|
|**2301**|Enable advanced decision support optimizations. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/920093).<br /><br />**Scope**: global and session and query|
|**2312**|Enables you to set the query optimizer cardinality estimation model to the [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] through [!INCLUDE[ssCurrent](../../includes/sscurrent-md.md)] versions, dependent of the compatibility level of the database. For more information, see [Microsoft Support article](http://support.microsoft.com/kb/2801413).<br /><br />Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1, to accomplish this at the query level, add the USE HINT 'FORCE_DEFAULT_CARDINALITY_ESTIMATION' [query hint](../../t-sql/queries/hints-transact-sql-query.md)  instead of using this trace flag.<br /><br />**Scope**: global or session or query| 
|**2335**|Causes [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] to assume a fixed amount of memory is available during query optimization. It does not limit the memory [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] grants to execute the query. The memory configured for [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] will still be used by data cache, query execution and other consumers. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2413549).<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Scope**: global or session or query|
|**2340**|Causes [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] not to use a sort operation (batch sort) for optimized Nested Loops joins when generating a plan. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2009160).<br /><br />Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1, to accomplish this at the query level, add the USE HINT 'DISABLE_OPTIMIZED_NESTED_LOOP' [query hint](../../t-sql/queries/hints-transact-sql-query.md)  instead of using this trace flag.<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Scope**: global or session or query|
|**2371**|Changes the fixed auto update statistics threshold to dynamic auto update statistics threshold. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2754171).<br /><br />**Note:** Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] and under the [database compatibility level](../../relational-databases/databases/view-or-change-the-compatibility-level-of-a-database.md) 130, this behavior is controlled by the engine and trace flag 2371 has no effect.<br /><br />**Scope**: global only|
|**2389**|Enable automatically generated quick statistics for ascending keys (histogram amendment). If trace flag 2389 is set, and a leading statistics column is marked as ascending, then the histogram used to estimate cardinality will be adjusted at query compile time. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2801413).<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Note:** This trace flag does not apply to CE version 120 or above. Use trace flag 4139 instead.<br /><br />**Scope**: global or session or query|
|**2390**|Enable automatically generated quick statistics for ascending or unknown keys (histogram amendment). If trace flag 2390 is set, and a leading statistics column is marked as ascending or unknown, then the histogram used to estimate cardinality will be adjusted at query compile time. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2801413).<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Note:** This trace flag does not apply to CE version 120 or above. Use trace flag 4139 instead.<br /><br />**Scope**: global or session or query|
|**2422**|Enables the [!INCLUDE[ssDEnoversion](../../includes/ssdenoversion-md.md)] to abort a request when the maximum time set by Resource Governor REQUEST_MAX_CPU_TIME_SEC configuration is exceeded. For more information, see this [Microsoft Support article](http://support.microsoft.com/help/4038419).<br /><br />**Note:** This trace flag applies to [!INCLUDE[ssSQL17](../../includes/sssql17-md.md)] CU3 and higher builds.<br /><br />**Scope**: global|
|**2430**|Enables alternate lock class cleanup. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2754301).<br /><br />**Scope**: global only| 
|**2453**|Allows a table variable to trigger recompile when enough number of rows are changed. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2952444).<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Scope**: global or session or query|
|**2469**|Enables alternate exchange for `INSERT INTO ... SELECT` into a partitioned columnstore index. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3204769).<br /><br />**Scope**: global or session or query|
|**2528**|Disables parallel checking of objects by DBCC CHECKDB, DBCC CHECKFILEGROUP, and DBCC CHECKTABLE. By default, the degree of parallelism is automatically determined by the query processor. The maximum degree of parallelism is configured just like that of parallel queries. For more information, see [Configure the max degree of parallelism Server Configuration Option](../../database-engine/configure-windows/configure-the-max-degree-of-parallelism-server-configuration-option.md).<br /><br />**Note:** Parallel DBCC checks should typically be enabled (default). The query processor reevaluates and automatically adjusts parallelism for each table or batch of tables checked by DBCC CHECKDB.<br /><br />The typical use scenario is when a system administrator knows that server load will increase before DBCC CHECKDB completes, and so chooses to manually decrease or disable parallelism, in order to increase concurrency with other user workload. However, disabling parallel checks in DBCC CHECKDB can cause it to take longer to complete.<br /><br />**Note:** If DBCC CHECKDB is executed using the TABLOCK option and parallelism is disabled, tables may be locked for longer periods of time.<br /><br />**Note:** Starting with [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] SP2, a MAXDOP option is available to override the max degree of parallelism configuration option of sp_configure for the statement.<br /><br />**Scope**: global or session|
|**2549**|Runs the DBCC CHECKDB command assuming each database file is on a unique disk drive. DBCC CHECKDB command builds an internal list of pages to read per unique disk drive across all database files. This logic determines unique disk drives based on the drive letter of the physical file name of each file.<br /><br />**Note:** Do not use this trace flag unless you know that each file is based on a unique physical disk.<br /><br />**Note:** Although this trace flag improve the performance of the DBCC CHECKDB commands which target usage of the PHYSICAL_ONLY option, some users may not see any improvement in performance. While this trace flag improves disk I/O resources usage, the underlying performance of disk resources may limit the overall performance of the DBCC CHECKDB command. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2634571).<br /><br />**Scope**: global only| 
|**2562**|Runs the DBCC CHECKDB command in a single "batch" regardless of the number of indexes in the database. By default, the DBCC CHECKDB command tries to minimize tempdb resources by limiting the number of indexes or "facts" that it generates by using a "batches" concept. This trace flag forces all processing into one batch.<br /><br />One effect of using this trace flag is that the space requirements for tempdb may increase. Tempdb may grow to as much as 5% or more of the user database that is being processed by the DBCC CHECKDB command.<br /><br />**Note:** Although this trace flag improve the performance of the DBCC CHECKDB commands which target usage of the PHYSICAL_ONLY option, some users may not see any improvement in performance. While this trace flag improves disk I/O resources usage, the underlying performance of disk resources may limit the overall performance of the DBCC CHECKDB command. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2634571).<br /><br />**Scope**: global only|
|**2566**|Runs the DBCC CHECKDB command without data purity check unless DATA_PURITY option is specified.<br /><br />**Note:** Column-value integrity checks are enabled by default and do not require the DATA_PURITY option. For databases upgraded from earlier versions of SQL Server, column-value checks are not enabled by default until DBCC CHECKDB WITH DATA_PURITY has been run error free on the database at least once. After this, DBCC CHECKDB checks column-value integrity by default. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/945770).<br /><br />**Scope**: global only|
|**3023**|Enables CHECKSUM option as default for BACKUP command. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2656988).<br /><br />**Note:** Starting with [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] this behavior is controlled by setting the **backup checksum default** configuration option. For more information, see [Server Configuration Options &#40;SQL Server&#41;](../../database-engine/configure-windows/server-configuration-options-sql-server.md).<br /><br />**Scope**: global and session|
|**3042**|Bypasses the default backup compression pre-allocation algorithm to allow the backup file to grow only as needed to reach its final size. This trace flag is useful if you need to save on space by allocating only the actual size required for the compressed backup. Using this trace flag might cause a slight performance penalty (a possible increase in the duration of the backup operation). For more information about the pre-allocation algorithm, see [Backup Compression &#40;SQL Server&#41;](../../relational-databases/backup-restore/backup-compression-sql-server.md).<br /><br />**Scope**: global only|
|**3051**|Enables SQL Server Backup to URL logging to a specific error log file. For more information, see [SQL Server Backup to URL Best Practices and Troubleshooting](../../relational-databases/backup-restore/sql-server-backup-to-url-best-practices-and-troubleshooting.md).<br /><br />**Scope**: global only|  
|**3205**|By default, if a tape drive supports hardware compression, either the DUMP or BACKUP statement uses it. With this trace flag, you can disable hardware compression for tape drivers. This is useful when you want to exchange tapes with other sites or tape drives that do not support compression.<br /><br />**Scope**: global or session|  
|**3226**|By default, every successful backup operation adds an entry in the [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] error log and in the system event log. If you create very frequent log backups, these success messages accumulate quickly, resulting in huge error logs in which finding other messages is problematic.<br /><br />With this trace flag, you can suppress these log entries. This is useful if you are running frequent log backups and if none of your scripts depend on those entries.<br /><br />**Scope**: global only|   
|**3427**|Enables fix for issue when many consecutive transactions inserting data into temp table in [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] or [!INCLUDE[ssSQL17](../../includes/sssql17-md.md)] consumes more CPU than in [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)]. For more information, see this [Microsoft Support article](http://support.microsoft.com/help/3216543)<br /><br />**Note:** This trace flag applies to [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1 CU2 and higher builds. Starting with [!INCLUDE[ssSQL17](../../includes/sssql17-md.md)] CU4 this trace flag has no effect.<br /><br />**Scope**: global only|  
|**3459**|Disables parallel redo. For more information, see this [Microsoft Support article](http://support.microsoft.com/help/3200975) and [Microsoft Support article](http://support.microsoft.com/help/4101554).<br /><br />**Note:** This trace flag applies to [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] and [!INCLUDE[ssSQL17](../../includes/sssql17-md.md)].<br /><br />**Scope**: global only| 
|**3608**|Prevents [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] from automatically starting and recovering any database except the **master** database. If activities that require **tempdb** are initiated, then **model** is recovered and **tempdb** is created. Other databases will be started and recovered when accessed. Some features, such as snapshot isolation and read committed snapshot, might not work. Use for [Move System Databases](../../relational-databases/databases/move-system-databases.md) and [Move User Databases](../../relational-databases/databases/move-user-databases.md).<br /><br />**Note:** Do not use during normal operation.<br /><br />**Scope**: global only|   
|**3625**|Limits the amount of information returned to users who are not members of the sysadmin fixed server role, by masking the parameters of some error messages using '\*\*\*\*\*\*'. This can help prevent disclosure of sensitive information.<br /><br />**Scope**: global only|  
|**4136**|Disables parameter sniffing unless OPTION(RECOMPILE), WITH RECOMPILE or OPTIMIZE FOR \<value> is used. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/980653). To accomplish this at the database level, see the PARAMETER_SNIFFING option in [ALTER DATABASE SCOPED CONFIGURATION &#40;Transact-SQL&#41;](../../t-sql/statements/alter-database-scoped-configuration-transact-sql.md). To accomplish this at the query level, add the OPTIMIZE FOR UNKNOWN [query hint](../../t-sql/queries/hints-transact-sql-query.md). Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1, a second option to accomplish this at the query level is to add the USE HINT 'PARAMETER_SNIFFING' [query hint](../../t-sql/queries/hints-transact-sql-query.md) instead of using this trace flag.<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Scope**: global or session|  
|**4137**|Causes [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] to generate a plan using minimum selectivity when estimating AND predicates for filters to account for correlation, under the query optimizer cardinality estimation model of [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] and earlier versions. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2658214).<br /><br />Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1, to accomplish this at the query level, add the USE HINT 'ASSUME_MIN_SELECTIVITY_FOR_FILTER_ESTIMATES' [query hint](../../t-sql/queries/hints-transact-sql-query.md) instead of using this trace flag when using the Legacy CE.<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Note:** This trace flag does not apply to CE version 120 or above. Use trace flag 9471 instead.<br /><br />**Scope**: global or session or query| 
|**4138**|Causes [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] to generate a plan that does not use row goal adjustments with queries that contain TOP, OPTION (FAST N), IN, or EXISTS keywords. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2667211).<br /><br />Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1, to accomplish this at the query level, add the USE HINT 'DISABLE_OPTIMIZER_ROWGOAL' [query hint](../../t-sql/queries/hints-transact-sql-query.md) instead of using this trace flag.<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Scope**: global or session or query| 
|**4139**|Enable automatically generated quick statistics (histogram amendment) regardless of key column status. If trace flag 4139 is set, regardless of the leading statistics column status (ascending, descending, or stationary), the histogram used to estimate cardinality will be adjusted at query compile time. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2952101).<br /><br />Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1, to accomplish this at the query level, add the USE HINT 'ENABLE_HIST_AMENDMENT_FOR_ASC_KEYS' [query hint](../../t-sql/queries/hints-transact-sql-query.md) instead of using this trace flag.<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Note:** This trace flag does not apply to CE version 70. Use trace flags 2389 and 2390 instead.<br /><br />**Scope**: global or session or query|
|**4199**|<a name="4199"></a>Enables query optimizer (QO) changes released in [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] Cumulative Updates and Service Packs.<br /><br />QO changes that are made to previous releases of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] are enabled by default under the latest database [compatibility level](../../t-sql/statements/alter-database-transact-sql-compatibility-level.md) in a given product release, without trace flag 4199 enabled.<br /><br />The following table summarizes the behavior when using specific database compatibility levels and trace flag 4199. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/974006).<br /><br /><table border="1" frame="void" width="550"><tr valign="middle" align="center"><td>**Database compatibility level**</td><td>**TF 4199**</td><td>**QO changes from previous database compatibility levels**</td><td>**QO changes for current version post-RTM**</td></tr><tr valign="middle" align="center"><td rowspan="2">**100 to 120**</td><td>Off</td><td>Disabled</td><td>Disabled</td></tr><tr valign="middle" align="center"><td>On</td><td>Enabled</td><td>Enabled</td></tr><tr valign="middle" align="center"><td rowspan="2">**130**</td><td>Off</td><td>Enabled</td><td>Disabled</td></tr><tr valign="middle" align="center"><td>On</td><td>Enabled</td><td>Enabled</td></tr><tr valign="middle" align="center"><td rowspan="2">**140**</td><td>Off</td><td>Enabled</td><td>Disabled</td></tr><tr valign="middle" align="center"><td>On</td><td>Enabled</td><td>Enabled</td></tr></table><br /><br />To accomplish this at the database level, see the QUERY_OPTIMIZER_HOTFIXES option in [ALTER DATABASE SCOPED CONFIGURATION &#40;Transact-SQL&#41;](../../t-sql/statements/alter-database-scoped-configuration-transact-sql.md).<br /><br />Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1, to accomplish this at the query level, add the USE HINT 'ENABLE_QUERY_OPTIMIZER_HOTFIXES' [query hint](../../t-sql/queries/hints-transact-sql-query.md) instead of using this trace flag.<br /><br />**Scope**: global or session or query|
|**4610**|Increases the size of the hash table that stores the cache entries by a factor of 8. When used together with trace flag 4618 increases the number of entries in the TokenAndPermUserStore cache store to 8,192. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/959823).<br /><br />**Scope:** global only|
|**4616**|Makes server-level metadata visible to application roles. In [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)], an application role cannot access metadata outside its own database because application roles are not associated with a server-level principal. This is a change of behavior from earlier versions of [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)]. Setting this global flag disables the new restrictions, and allows for application roles to access server-level metadata.<br /><br />**Scope**: global only|
|**4618**|Limits the number of entries in the TokenAndPermUserStore cache store to 1,024. When used together with trace flag 4610 increases the number of entries in the TokenAndPermUserStore cache store to 8,192. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/959823).<br /><br />**Scope:** global only|
|**5004**|Pauses TDE encryption scan and causes encryption scan worker to exit without doing any work. The database will continue to be in encrypting state (encryption in progress). To resume re-encryption scan, disable trace flag 5004 and run ALTER DATABASE <database_name> SET ENCRYPTION ON. <br /><br />**Scope:** global only|
|**6498**|Enables more than one large query compilation to gain access to the big gateway when there is sufficient memory available. It is based on the 80 percentage of SQL Server Target Memory, and it allows for one large query compilation per 25 gigabytes (GB) of memory. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3024815).<br /><br />**Note:** Starting with [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] SP2 and [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] this behavior is controlled by the engine and trace flag 6498 has no effect.<br /><br />**Scope**: global only|
|**6527**|Disables generation of a memory dump on the first occurrence of an out-of-memory exception in CLR integration. By default, [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] generates a small memory dump on the first occurrence of an out-of-memory exception in the CLR. The behavior of the trace flag is as follows:<br /><br />-   If this is used as a startup trace flag, a memory dump is never generated. However, a memory dump may be generated if other trace flags are used.<br />-   If this trace flag is enabled on a running server, a memory dump will not be automatically generated from that point on. However, if a memory dump has already been generated due to an out-of-memory exception in the CLR, this trace flag will have no effect.<br /><br />**Scope**: global only|
|**6532**|Enables performance improvement of query operations with spatial data types in [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] and [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)]. The performance gain will vary, depending on the configuration, the types of queries, and the objects. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3107399).<br /><br />**Note:** Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] this behavior is controlled by the engine and trace flag 6532 has no effect.<br /><br />**Scope**: global and session|
|**6533**|Enables performance improvement of query operations with spatial data types in [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] and [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)]. The performance gain will vary, depending on the configuration, the types of queries, and the objects. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3107399).<br /><br />**Note:** Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] this behavior is controlled by the engine and trace flag 6533 has no effect.<br /><br />**Scope**: global and session| 
|**6534**|Enables performance improvement of query operations with spatial data types in [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)], [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] and [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)]. The performance gain will vary, depending on the configuration, the types of queries, and the objects. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3107399).<br /><br />**Scope**: global and session|
|**7314**|Forces NUMBER values with unknown precision/scale to be treated as double values with OLE DB provider. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3051993).<br /><br />**Scope**: global and session|  
|**7412**|Enables the lightweight query execution statistics profiling infrastructure. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3170113).<br /><br />**Scope**: global only|
|**7471**|Enables running multiple [UPDATE STATISTICS](../../t-sql/statements/update-statistics-transact-sql.md) for different statistics on a single table concurrently. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3156157).<br /><br />**Note:** This trace flag applies to [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] SP1 and higher builds.<br /><br />**Scope**: global only|
|**7745**|Forces Query Store to not flush data to disk on database shutdown.<br /><br />**Note:** Using this trace may cause Query Store data not previously flushed to disk to be lost in case of shutdown. For a [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] shutdown, the command SHUTDOWN WITH NOWAIT can be used instead of this trace flag to force an immediate shutdown.<br /><br />**Scope**: global only|
|**7752**|Enables asynchronous load of Query Store.<br /><br />**Note:** Use this trace flag if [!INCLUDE[ssNoVersion](../../includes/ssNoVersion-md.md)] is experiencing high number of QDS_LOADDB waits related to Query Store synchronous load (default behavior).<br /><br />**Scope**: global only|
|**7806**|Enables a dedicated administrator connection (DAC) on [!INCLUDE[ssExpress](../../includes/ssexpress-md.md)]. By default, no DAC resources are reserved on [!INCLUDE[ssExpress](../../includes/ssexpress-md.md)]. For more information, see [Diagnostic Connection for Database Administrators](../../database-engine/configure-windows/diagnostic-connection-for-database-administrators.md).<br /><br />**Scope**: global only|  
|**8011**|Disable the ring buffer for Resource Monitor. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/920093).<br /><br />**Scope**: global and session|
|**8012**|Disable the ring buffer for schedulers. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/920093).<br /><br />**Scope**: global only|
|**8015**|Disable auto-detection and NUMA setup. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2813214).<br /><br />**Scope**: global only|
|**8018**|Disable the exception ring buffer. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/920093).<br /><br />**Scope**: global only|
|**8019**|Disable stack collection for the exception ring buffer. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/920093).<br /><br />**Scope**: global only|
|**8020**|Disable working set monitoring. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/920093).<br /><br />**Scope**: global only|
|**8032**|Reverts the cache limit parameters to the [!INCLUDE[ssVersion2005](../../includes/ssversion2005-md.md)] RTM setting which in general allows caches to be larger. Use this setting when frequently reused cache entries do not fit into the cache and when the [optimize for ad hoc workloads Server Configuration Option](../../database-engine/configure-windows/optimize-for-ad-hoc-workloads-server-configuration-option.md) has failed to resolve the problem with plan cache.<br /><br />**WARNING:** Trace flag 8032 can cause poor performance if large caches make less memory available for other memory consumers, such as the buffer pool.<br /><br />**Scope**: global only|   
|**8048**|Converts NUMA partitioned memory objects into CPU partitioned. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2809338).<br /><br />**Note:** Starting with [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] SP2 and [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] this behavior is controlled by the engine and trace flag 8048 has no effect.<br /><br />**Scope**: global only|  
|**8075**|Reduces [VAS](../../relational-databases/memory-management-architecture-guide.md#changes-to-memory-management-starting-with-includesssql11includessssql11-mdmd) fragmentation when you receive memory page allocation errors on a 64-bit [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] or [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)]. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3074434).<br /><br />**Note:** This trace flag applies to [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)], [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] RTM CU10, and [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] SP1 CU3. Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] this behavior is controlled by the engine and trace flag 8075 has no effect.<br /><br />**Scope**: global only|
|**8079**|Allows [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] SP2 to interrogate the hardware layout and automatically configure Soft-NUMA on systems reporting 8 or more CPUs per NUMA node. The automatic Soft-NUMA behavior is Hyperthread (HT/logical processor) aware. The partitioning and creation of additional nodes scales background processing by increasing the number of listeners, scaling and network and encryption capabilities.<br /><br />**Note:** This trace flag applies to [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] SP2. Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] this behavior is controlled by the engine and trace flag 8048 has no effect.<br /><br />**Scope**: global only| 
|**8207**|Enables singleton updates for Transactional Replication. Updates to subscribers can be replicated as a DELETE and INSERT pair. This might not meet business rules, such as firing an UPDATE trigger. With trace flag 8207 an update to a unique column that affects only one row (a singleton update) is replicated as an UPDATE and not as a DELETE or INSERT pair. If the update affects a column on which has a unique constraint or if the update affects multiple rows, the update is still replicated as a DELETE or INSERT pair. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/302341).<br /><br />**Scope**: global only|
|**8721**|Reports to the error log when auto-update statistics executes. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/195565).<br /><br />**Scope**: global only|
|**8744**|Disable pre-fetching for the Nested Loop operator. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/920093).<br /><br />**Note:**  Incorrect use of this trace flag may cause additional physical reads when [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] executes plans that contain the Nested Loops operator.<br /><br />**Scope**: global and session|
|**9024**|Converts a global log pool memory object into NUMA node partitioned memory object. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/2809338).<br /><br />**Note:** Starting with [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] SP3 and [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] SP1 this behavior is controlled by the engine and trace flag 9024 has no effect.<br /><br />**Scope**: global only|
|**9347**|Disables batch mode for sort operator. [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] introduced a new batch mode sort operator that boosts performance for many analytical queries. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3172787).<br /><br />**Scope**: global or session or query|
|**9349**|Disables batch mode for top N sort operator. [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] introduced a new batch mode top sort operator that boosts performance for many analytical queries.<br /><br />**Scope**: global or session or query|
|**9389**|Enables dynamic memory grant for batch mode operators. If a query does not get all the memory it needs, it spills data to tempdb, incurring additional I/O and potentially impacting query performance. If the dynamic memory grant trace flag is enabled, a batch mode operator may ask for additional memory and avoid spilling to tempdb if additional memory is available.<br /><br />**Scope**: global or session| 
|**9398**|Disables [Adaptive Join](../../relational-databases/performance/adaptive-query-processing.md#batch-mode-adaptive-joins) operator that enables the choice of a [Hash join or Nested Loops join](../../relational-databases/performance/joins.md) method to be deferred until the after the first input has been scanned, as introduced in [!INCLUDE[ssSQL17](../../includes/sssql17-md.md)]. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/4099126).<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Scope**: global and session and query|
|**9453**|Disables batch mode execution. For more information, see this [Microsoft Support article](http://support.microsoft.com/help/4016902).<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Scope:** global and session and query|
|**9471**|Causes [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] to generate a plan using minimum selectivity for single-table filters, under the query optimizer cardinality estimation model of [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] through [!INCLUDE[ssCurrent](../../includes/sscurrent-md.md)] versions.<br /><br />Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1, to accomplish this at the query level, add the USE HINT 'ASSUME_MIN_SELECTIVITY_FOR_FILTER_ESTIMATES' [query hint](../../t-sql/queries/hints-transact-sql-query.md) instead of using this trace flag.<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Note:** This trace flag does not apply to CE version 70. Use trace flag 4137 instead.<br /><br />**Scope**: global or session or query| 
|**9476**|Causes [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)] to generate a plan using the Simple Containment assumption instead of the default Base Containment assumption, under the query optimizer cardinality estimation model of [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)] through [!INCLUDE[ssCurrent](../../includes/sscurrent-md.md)] versions. For more information, see this  [Microsoft Support article](http://support.microsoft.com/kb/3189675).<br /><br />Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1, to accomplish this at the query level, add the USE HINT 'ASSUME_JOIN_PREDICATE_DEPENDS_ON_FILTERS' [query hint](../../t-sql/queries/hints-transact-sql-query.md) instead of using this trace flag.<br /><br />**Note:** Please ensure that you thoroughly test this option, before rolling it into a production environment.<br /><br />**Scope**: global or session or query| 
|**9481**|Enables you to set the query optimizer cardinality estimation model to the [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] and earlier versions, irrespective of the compatibility level of the database. For more information, see [Microsoft Support article](http://support.microsoft.com/kb/2801413). To accomplish this at the database level, see the LEGACY_CARDINALITY_ESTIMATION option in [ALTER DATABASE SCOPED CONFIGURATION &#40;Transact-SQL&#41;](../../t-sql/statements/alter-database-scoped-configuration-transact-sql.md).<br /><br />Starting with [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)] SP1, to accomplish this at the query level, add the USE HINT 'FORCE_LEGACY_CARDINALITY_ESTIMATION' [query hint](../../t-sql/queries/hints-transact-sql-query.md) instead of using this trace flag.<br /><br />**Scope**: global or session or query|  
|**9485**|Disables SELECT permission for DBCC SHOW_STATISTICS.<br /><br />**Scope**: global only|
|**9488**|Sets the fixed estimation for Table Valued Functions to the default of 1 (corresponding to the default under the query optimizer cardinality estimation model of [!INCLUDE[ssKilimanjaro](../../includes/ssKilimanjaro-md.md)] and earlier versions), when using the query optimizer cardinality estimation model of [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] through [!INCLUDE[ssCurrent](../../includes/sscurrent-md.md)] versions.<br /><br />**Scope**: global or session or query|
|**9495**|Disables parallelism during insertion for INSERT...SELECT operations and it applies to both user and temporary tables. For more information, see [Microsoft Support article](http://support.microsoft.com/kb/3180087)<br /><br />**Scope**: global or session| 
|**9567**|Enables compression of the data stream for Always On Availability Groups during automatic seeding. Compression can significantly reduce the transfer time during automatic seeding and will increase the load on the processor. For more information, see [Automatically initialize Always On availability group](../../database-engine/availability-groups/windows/automatically-initialize-always-on-availability-group.md) and [Tune compression for availability group](../../database-engine/availability-groups/windows/tune-compression-for-availability-group.md).<br /><br />**Scope**: global or session|
|**9591**|Disables log block compression in Always On Availability Groups. Log block compression is the default behavior used with both synchronous and asynchronous replicas in [!INCLUDE[ssSQL11](../../includes/sssql11-md.md)] and [!INCLUDE[ssSQL14](../../includes/sssql14-md.md)]. In [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)], compression is only used with asynchronous replica. <br /><br />**Scope**: global or session|
|**9592**|Enables log stream compression for synchronous availability groups. This feature is disabled by default on synchronous availability groups because compression adds latency. For more information, see [Tune compression for availability group](../../database-engine/availability-groups/windows/tune-compression-for-availability-group.md).<br /><br />**Scope**: global or session| 
|**9929**|Reduces the In-Memory checkpoint files to 1 MB each. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/3147012).<br /><br />**Scope**: global only|  
|**9939**|Enables parallel plans and parallel scan of memory-optimized tables and table variables in DML operations that reference memory-optimized tables or table variables, as long as they are not the target of the DML operation in [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)]. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/4013877).<br /><br />**Note:** Trace flag 9939 is not needed if trace flag 4199 is also explicitly enabled.<br /><br />**Scope**: global or session or query|   
|**10204**|Disables merge/recompress during columnstore index reorganization. In [!INCLUDE[ssSQL15](../../includes/sssql15-md.md)], when a columnstore index is reorganized, there is new functionality to automatically merge any small compressed rowgroups into larger compressed rowgroups, as well as recompressing any rowgroups that have a large number of deleted rows.<br /><br />**Note:** Trace flag 10204 does not apply to columnstore indexes which are created on memory-optimized tables.<br /><br />**Scope**: global or session|   
|**10316**|Enables creation of additional indexes on [internal memory-optimized staging temporal table](../../relational-databases/tables/system-versioned-temporal-tables-with-memory-optimized-tables.md), beside the default one. If you have specific query pattern that includes columns which are not covered by the default index you may consider adding additional ones.<br /><br />**Note:** System-versioned temporal tables for Memory-Optimized Tables are designed to provide high transactional throughput. Please be aware that creating additional indexes may introduce overhead for DML operations that update or delete rows in the current table. With the additional indexes you should aim to find the right  balance between performance of temporal queries and additional DML overhead.<br /><br />**Scope**: global or session|
|**11023**|Disables the use of the last persisted sample rate, for all subsequent statistics update where a sample rate is not specified explicitly as part of the [UPDATE STATISTICS](../../t-sql/statements/update-statistics-transact-sql.md) statement. For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/4039284).<br /><br />**Scope**: global or session|    
|**11024**|Enables triggering the auto update of statistics when the modification count of any partition exceeds the local [threshold](../../relational-databases/statistics/statistics.md#AutoUpdateStats). For more information, see this [Microsoft Support article](http://support.microsoft.com/kb/4041811).<br /><br />**Scope**: global or session| 
  
## Remarks  
 In [!INCLUDE[ssNoVersion](../../includes/ssnoversion-md.md)], there are three types of trace flags: query, session and global. Query trace flags are active for the context of a specific query. Session trace flags are active for a connection and are visible only to that connection. Global trace flags are set at the server level and are visible to every connection on the server. Some flags can only be enabled as global, and some can be enabled at either global or session scope.  
  
 The following rules apply:  
-   A global trace flag must be enabled globally. Otherwise, the trace flag has no effect. We recommend that you enable global trace flags at startup, by using the **-T** command line option. This ensures the trace flag remains active after a server restart.  
-   If a trace flag has either global, session or query scope, it can be enabled with the appropriate scope. A trace flag that is enabled at the session level never affects another session, and the effect of the trace flag is lost when the SPID that opened the session logs out.  
  
Trace flags are set on or off by using either of the following methods:
-   Using the DBCC TRACEON and DBCC TRACEOFF commands.  
     For example, to enable the 2528 trace flag globally, use [DBCC TRACEON](../../t-sql/database-console-commands/dbcc-traceon-transact-sql.md) with the -1 argument: `DBCC TRACEON (2528, -1)`. The effect of enabling a global trace flag with DBCC TRACEON is lost on server restart. To turn off a global trace flag, use [DBCC TRACEOFF](../../t-sql/database-console-commands/dbcc-traceoff-transact-sql.md) with the -1 argument.  
-   Using the **-T** startup option to specify that the trace flag be set on during startup.  
     The **-T** startup option enables a trace flag globally. You cannot enable a session-level trace flag by using a startup option. This ensures the trace flag remains active after a server restart. For more information about startup options, see [Database Engine Service Startup Options](../../database-engine/configure-windows/database-engine-service-startup-options.md).
-   At the query level, by using the QUERYTRACEON [query hint](http://support.microsoft.com/kb/2801413).
  
Use the `DBCC TRACESTATUS` command to determine which trace flags are currently active.
  
## Examples  
 The following example sets trace flag 3205 on for all sessions at the server level by using DBCC TRACEON.  
  
```sql  
DBCC TRACEON (3205,-1);  
```

You can enable all plan-affecting hotfixes controlled by trace flags 4199 and 4137 for a particular query.
  
```sql
SELECT x FROM correlated WHERE f1 = 0 AND f2 = 1 OPTION (QUERYTRACEON 4199, QUERYTRACEON 4137)
``` 
 
## See Also  
[Data Types &#40;Transact-SQL&#41;](../../t-sql/data-types/data-types-transact-sql.md)  
[DBCC INPUTBUFFER &#40;Transact-SQL&#41;](../../t-sql/database-console-commands/dbcc-inputbuffer-transact-sql.md)  
[DBCC OUTPUTBUFFER &#40;Transact-SQL&#41;](../../t-sql/database-console-commands/dbcc-outputbuffer-transact-sql.md)  
[DBCC TRACEOFF &#40;Transact-SQL&#41;](../../t-sql/database-console-commands/dbcc-traceoff-transact-sql.md)  
[DBCC TRACEON &#40;Transact-SQL&#41;](../../t-sql/database-console-commands/dbcc-traceon-transact-sql.md)  
[DBCC TRACESTATUS &#40;Transact-SQL&#41;](../../t-sql/database-console-commands/dbcc-tracestatus-transact-sql.md)  
[EXECUTE &#40;Transact-SQL&#41;](../../t-sql/language-elements/execute-transact-sql.md)  
[SELECT &#40;Transact-SQL&#41;](../../t-sql/queries/select-transact-sql.md)  
[SET NOCOUNT &#40;Transact-SQL&#41;](../../t-sql/statements/set-nocount-transact-sql.md)  
[ALTER DATABASE SET Options &#40;Transact-SQL&#41;](../../t-sql/statements/alter-database-transact-sql-set-options.md)  
[ALTER DATABASE SCOPED CONFIGURATION &#40;Transact-SQL&#41;](../../t-sql/statements/alter-database-scoped-configuration-transact-sql.md)  
[Query Hints (Transact-SQL)](../../t-sql/queries/hints-transact-sql-query.md)