Simon's SQL

SQL,DBA,tuning,Trouble Shooting,Performance

SQL Server Trace Flags

Posted by Simon Cho on 04/12/2011

lag Trace Flag Description (underlined are sp_configure’able)
-1 Sets trace flags for all connections. Used only with DBCC TRACEON and TRACEOFF. The setting of the Trace flag -1 is not visible with DBCC TRACESTATUS command, but work without problems.
105 SQL Server 6.5 you can use maximum 16 tables or subqueries in a single select statement. There is no documented way, to avoid this restriction, but you can use undocumented trace flag 105 for this purpose.
106 Disables line number information for syntax errors.
107 Interprets numbers with a decimal point as float instead of decimal.
110 Turns off ANSI select characteristics.
204 A backward compatibility switch that enables non-ansi standard behavior. E.g. previously SQL server ignored trailing blanks in the like statement and allowed queries that contained aggregated functions to have items in the group by clause that were not in the select list.
205 Report when a statistics-dependent stored procedure is being recompiled as a result of AutoStat.
206 Provides backward compatibility for the setuser statement.
208 SET QUOTED IDENTIFIER ON.
237 Tells SQL Server to use correlated sub-queries in Non-ANSI standard backward compatibility mode.
242 Provides backward compatibility for correlated subqueries where non-ANSI-standard results are desired.
243 The behavior of SQL Server is now more consistent because null ability checks are made at run time and a null ability violation results in the command terminating and the batch or transaction process continuing.
244 Disables checking for allowed interim constraint violations. By default, SQL Server checks for and allows interim constraint violations. An interim constraint violation is caused by a change that removes the violation such that the constraint is met, all within a single statement and transaction. SQL Server checks for interim constraint violations for self-referencing DELETE statements, INSERT, and multi-row UPDATE statements. This checking requires more work tables. With this trace flag you can disallow interim constraint violations, thus requiring fewer work tables.
246 Derived or NULL columns must be explicitly named in a select….INTO or create view statement when not done they raise an error. This flag avoids that.
253 Prevents ad-hoc query plans to stay in cache.
257 Will invoke a print algorithm on the XML output before returning it to make the XML result more readable.
260 Prints versioning information about extended stored procedure dynamic-link libraries (DLLs). For more information about __GetXpVersion(), see Creating Extended Stored Procedures. Scope: global or session
262 SQL 7 – Trailing spaces are no longer truncated from literal strings in CASE statements. Used after hotfix 891116
302 Should be used with flag 310 to show the actual join ordering. Prints information about whether the statistics page is used, the actual selectivity (if available), and what SQL Server estimated the physical and logical I/O would be for the indexes.
310 Prints information about join order. Index selection information is also available in a more readable format using SET SHOWPLAN_ALL, as described in the SET statement.
320 Disables join-order heuristics used in ANSI joins. To see join-order heuristics use flag 310. SQL Server uses join-order heuristics to reduce the no’ of permutations when using the best join order.
323 Reports on the use of update statements using UPDATE in place. Shows a detailed description of the various update methods used by SQL Server 6.5.
325 Prints information about the cost of using a non-clustered index or a sort to process an ORDER BY clause.
326 Prints information about the estimated & actual costs of sorts. Instructs the server to use arithmetic averaging when calculating density instead of a geometric weighted average when updating statistics.  Useful for building better stats when an index has skew on the leading column.  Use only for updating the stats of a table/index with known skewed data.
330 Enables full output when using the SET SHOWPLAN_ALL option, which gives detailed information about joins.
342 Disables the costing of pseudo-merge joins, thus significantly reducing time spent on the parse for certain types of large, multi-table joins. One can also use SET FORCEPLAN ON to disable the costing of pseudo-merge joins because the query is forced to use the order specified in the FROM clause.
345 Increase the accuracy of choice of optimum order when you join 6 or more tables.
506 Enforces SQL-92 standards regarding null values for comparisons between variables and parameters. Any comparison of variables and parameters that contain a NULL always results in a NULL.
610 SQL 10 – Enable the potential for minimal-logging when:
·   Bulk loading into an empty clustered index, with no nonclustered indexes
·   Bulk loading into a non-empty heap, with no nonclustered indexes
611 After SQL 9 when turned on, each lock escalation is recorded in the SQL Server error log along with the SQL Server handle number.
652 Disables read ahead for the server.
653 Disables read ahead for the current connection.
661 Disables the ghost record removal process. A ghost record is the result of a delete operation. When you delete a record, the deleted record is kept as a ghost record. Later, the deleted record is purged by the ghost record removal process. When you disable this process, the deleted record is not purged. Therefore, the space that the deleted record consumes is not freed. This behavior affects space consumption and the performance of scan operations. SCOPE: Global. If you turn off this trace flag, the ghost record removal process works correctly.
806 Cause ‘DBCC-style’ page auditing to be performed whenever a database page is read into the buffer pool. This is useful to catch cases where pages are being corrupted in memory and then written out to disk with a new page checksum. When they’re read back in the checksum will look correct, but the page is corrupt (because of the previous memory corruption). This page auditing goes someway to catching this – especially on non-Enterprise Edition systems that don’t have the ‘checksum sniffer’.
809 SQL 8 – Limits the amount of Lazy Write activity.
815 Enables latch enforcement. SQL Server 8 (with service pack 4) and SQL Server 9 can perform latch enforcement for data pages found in the buffer pool cache. Latch enforcement changes the virtual memory protection state while database page status changes from “clean” to “dirty” (“dirty” means modified through INSERT, UPDATE or DELETE operation). If an attempt is made to modify a data page while latch enforcement is set, it causes an exception and creates a mini-dump in SQL Server installation’s LOG directory. Microsoft support can examine the contents of such mini-dump to determine the cause of the exception. In order to modify the data page the connection must first acquire a modification latch. Once the data modification latch is acquired the page protection is changed to read-write. Once the modification latch is released the page protection changes back to read-only.
818 SQL 8 enables in memory ring buffer used to track last 2048 successful write operations.
830 SQL 9 – disable the reporting of CPU Drift errors in the SQL Server errorlog like SQL Server has encountered 2 occurrence(s) of I/O requests taking longer than 15 seconds to complete
834 Causes SQL Server to use Windows large-page allocations for the memory that is allocated for the buffer pool. The page size varies depending on the hardware platform, but the page size may be from 2 MB to 16 MB. Large pages are allocated at startup and are kept throughout the lifetime of the process. Trace flag 834 improves performance by increasing the efficiency of the translation look-aside buffer (TLB) in the CPU.
Flag 834 applies only to 64-bit versions of SQL Server. You must have the Lock pages in memory user right to turn on trace flag 834. You can turn on trace flag 834 only at startup.
Trace flag 834 may prevent the server from starting if memory is fragmented and if large pages cannot be allocated. Therefore, trace flag 834 is best suited for servers that are dedicated to SQL Server.
For more information about large-page support, http://msdn2.microsoft.com/en-us/library/aa366720.aspx(http://msdn2.microsoft.com/en-us/library/aa366720.aspx)
835 SQL 9 & 10. For 64 bit SQL Server. This turns off Lock pages in memory.
836 Causes SQL Server to size the buffer pool at startup based on the value of the max server memory option instead of based on the total physical memory. You can use trace flag 836 to reduce the number of buffer descriptors that are allocated at startup in 32-bit Address Windowing Extensions (AWE) mode.
Trace flag 836 applies only to 32-bit versions of SQL Server that have the AWE allocation enabled. You can turn on trace flag 836 only at startup.
845 SQL 9 & 10. For 64 bit SQL Server. This turns on Lock pages in memory.
1117 Grows all data files at once, else it goes in turns.
1118 Switches allocations in tempDB from 1pg at a time (for first 8 pages) to one extent. There is now a cache of temp tables. When a new temp table is created on a cold system it uses the same mechanism as for SQL 8. When it is dropped though, instead of all the pages being deallocated completely, one IAM page & one data page are left allocated, then the temp table is put into a special cache. Subsequent temp table creations will look in the cache to see if they can just grab a pre-created temp table. If so, this avoids accessing the allocation bitmaps completely. The temp table cache isn’t huge (32 tables), but this can still lead to a big drop in latch contention in tempdb. http://www.sqlskills.com/BLOGS/PAUL/post/Misconceptions-around-TF-1118.aspx
1180 Forces allocation to use free pages for text or image data and maintain efficiency of storage. 1197 applies only in the case of SQL 7 – SP3. Helpful in case when DBCC SHRINKFILE and SHRINKDATABASE commands may not work because of sparsely populated text, ntext, or image columns
1197
1200 Prints lock information (the process ID and type of lock requested).
1202 Insert blocked lock requests into syslocks.
1204 Returns resources and types of locks participating in a deadlock and command affected. Scope: global only
1205 More detailed information about the command being executed at the time of a deadlock. This trace flag was documented in SQL Server 7.0 Books Online, but was not documented in SQL Server 8.
1206 Used to complement flag 1204 by displaying other locks held by deadlock parties
1211 Disables lock escalation based on memory pressure, or based on number of locks. The SQL Server Database Engine will not escalate row or page locks to table locks.
Using this trace flag can generate excessive numbers of locks. This can slow the performance of the Database Engine, or cause 1204 errors (unable to allocate lock resource) because of insufficient memory. For more information, see Lock Escalation (Database Engine).
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. Scope: global or session
1216 SQL 7 – Disables Health reporting. Lock monitor when detects a (worker thread) resource level blocking scenario. If a SPID that owns a lock is currently queued to the scheduler, because all the assigned worker threads have been created and all the assigned worker threads are in an un-resolvable wait state, the following error message is written to the SQL Server error log:
Error 1223: Process ID %d:%d cannot acquire lock “%s” on resource %s because a potential deadlock exists on Scheduler %d for the resource. Process ID %d:% d holds a lock “%h” on this resource.
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. Scope: global only
1224 Disables lock escalation based on the number of locks. However, memory pressure can still activate lock escalation. The Database Engine 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:
·   40% of the memory that is used by Db Engine, exclusive of memory allocation using Address Windowing Extension (AWE). This is applicable when the locks parameter of sp_configure is set to 0.
·   Forty percent of the lock memory that is configured by using the locks parameter of sp_configure.
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.
Note:Lock escalation to the table- or HoBT-level granularity can also be controlled by using the LOCK_ESCALATION option of the ALTER TABLE statement.  Scope:global or session
1261 SQL 8 – Disables Health reporting. Lock monitor when detects a (worker thread) resource level blocking scenario. If a SPID that owns a lock is currently queued to the scheduler, because all the assigned worker threads have been created and all the assigned worker threads are in an un-resolvable wait state, the following error message is written to the SQL Server error log:
Error 1229: Process ID %d:%d owns resources that are blocking processes on scheduler %d.
1400 Enables the creation of the database mirroring endpoint, which is required for setting up and using database mirroring. This trace flag is allowed only when using the –T.
1462 Turns off log stream compression and effectively reverts the behavior back to ver 9.
1603 Use standard disk I/O (i.e. turn off asynchronous I/O).
1609 Turns on the unpacking and checking of remote procedure call (RPC) information in Open Data Services. Used only when applications depend on the old behavior.
1610 Boot the SQL dataserver with TCP_NODELAY enabled.
1611 If possible, pin shared memory — check errorlog for success/failure.
1704 Prints information when a temporary table is created or dropped.
1717 Causes new objects being created to be system objects.
1806 Disables instant file initialization.
1807 Allows creating a database file on a mapped or UNC network location. unsupported under SQL Server 7 & 8.
2301 Enables advanced optimizations that are specific to decision support queries. This option applies to decision support processing of large data sets.
2330 Stops the collection of statistics for sys.db_index_usage_stats.
2382 Statistics collected for system tables.
2389 SQL 9 – Tracks the nature of columns by subsequent statistics updates. When SQL Server determines that the statistics increase three times, the column is branded ascending. The statistics will be updated automatically at query compile.
2390 Does the same like 2389 even if ascending nature of the column is not known and — never enable without 2389.
2440 Parallel query execution strategy on partitioned tables. SQL 9 – uses a single thread per partition parallel query execution strategy. In ver. 10, multiple threads can be allocated to a single partition, thus improving the query’s response time.
2505 Prevents DBCC TRACEON 208, SPID 10 errors from appearing in the error log.
2508 Disables parallel non-clustered index checking for DBCC CHECKTABLE.
2509 Used with DBCC CHECKTABLE.html to see the total count of ghost records in a table
2520 Force DBCC HELP to return syntax of undocumented DBCC statements. If 2520 is not turned on, DBCC HELP will refuse to give you the syntax stating: “No help available for DBCC statement ‘undocumented statement'”.
2528 Disables parallel checking of objects by DBCC CHECKDB, CHECKFILEGROUP and 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 max degree of parallelism Option.
Parallel DBCC should typically be left enabled. For DBCC CHECKDB, the query processor reevaluates and automatically adjusts parallelism with each table or batch of tables checked. Sometimes, checking may start when the server is almost idle. An administrator who knows that the load will increase before checking is complete may want to manually decrease or disable parallelism.
Disabling parallel checking of DBCC can cause it to take much longer to complete and if DBCC is run with the TABLOCK feature enabled and parallelism set off, tables may be locked for longer periods of time.
Scope: global or session
2537 SQL 9 & 10. Allows function ::fn_dblog to look inside all logs (not just the active log).
2542 SQL 8 – Used with Sqldumper.exe to get certain dumps. In range 254x – 255x.
2551 Adds additional information to the dump file.
2701 Sets the @@ERROR system function to 50000 for RAISERROR messages with severity levels of 10 or less. When disabled, sets the @@ERROR system function to 0 for RAISERROR messages with severity levels of 10 or less.
2861 Cache query plans for queries that have a cost of zero or near to zero.
3001 Stops sending backup entries into MSDB.
3004 Gives out more detailed information about restore & backup activities.
3031 SQL 9 – will turn the NO_LOG and TRUNCATE_ONLY options into checkpoints in all recovery modes.
3104 Causes SQL Server to bypass checking for free space.
3111 Cause LogMgr::ValidateBackedupBlock to be skipped during backup and restore operations.
3205 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. Scope: global or session
3213 Trace SQL Server activity during backup process so that we will come to know which part of backup process is taking more time.
3222 Disables the read ahead that is used by the recovery operation during roll forward operations.
3226 With this trace flag, you can suppress BACKUP COMPLETED log entries going to WIN and SQL logs.
3231 SQL 8 & 9 – will turn the NO_LOG and TRUNCATE_ONLY options into no-ops in FULL/BULK_LOGGED recovery mode, and will clear the log in SIMPLE recovery mode.
3282 SQL 6.5 – Used after backup restoration fails refer to microsoft for article Q215458.
3422 Cause auditing of transaction log records as they’re read (during transaction rollback or log recovery). This is useful because there is no equivalent to page checksums for transaction log records and so no way to detect whether log records are being corrupted e careful with these trace flags – I don’t recommend using them unless you are experiencing corruptions that you can’t diagnose. Turning them on will cause a big CPU hit because of the extra auditing that’s happening.
3502 Tracks CHECKPOINT – Prints a message to the log at the start and end of each checkpoint.
3503 Indicates whether the checkpoint at the end of automatic recovery was skipped for a database (this applies only to read-only databases).
3504 For internal testing. Will raise a bogus log-out-of-space condition from checkpoint()
3505 Disables automatic checkpoints. May increase recovery time and can prevent log space reuse until the next checkpoint is issued. Make sure to issue manual checkpoints on all read/write databases at appropriate time intervals.
Note does not prevent the internal checkpoints that are issued by certain commands, such as BACKUP.
3601 Stack trace when error raised. Also see 3603
3602 Records all error and warning messages sent to the client.
3603 SQL Server fails to install on tricore, Bypass SMT check is enabled, flags are added via registry. Also see 3601.
3604 Sends trace output to the client. This trace flag is used only when setting trace flags with DBCC TRACEON and DBCC TRACEOFF.
3605 Sends trace output to the error log.  (if SQL Server is started from CMD output also appears on the screen)
3607 Trace flag 3607 skips the recovery of databases on the startup of SQL Server and clears the TempDB. Setting this flag lets you get past certain crashes, but there is a chance that some data will be lost
3608 Prevents SQL Server from automatically starting and recovering any database except the master database. Databases will be started and recovered when accessed. Some features, such as snapshot isolation and read committed snapshot, might not work.
3609 Skips the creation of the tempdb database at startup. Use this trace flag if the device or devices on which tempdb resides are problematic or problems exist in the model database.
3610 SQL 9. Divide by zero to result in NULL instead of error.
3625 Limits the amount of information returned in error messages. For more information, see Metadata Visibility Configuration. Scope: global only
3626 Turns on tracking of the CPU data for the sysprocesses table.
3640 Eliminates the sending of DONE_IN_PROC messages to the client for each statement in a stored procedure. This is similar to the session setting of SET NOCOUNT ON, but when set as a trace flag, every client session is handled this way.
3689 Logs extended errors to errorlog when network disconnect occurs, turned off by default. Will dump out the socket error code this can sometimes give you a clue as to the root cause.
3913 SQL 7/8 – SQL Server does not update the rowcnt column of the sysindexes system table until the transaction is committed. When turned on the optimizer gets row count information from in-memory metadata that is saved to sysindexes system table when the transaction commits.
4013 This trace flag writes an entry to the SQL Server error log when a new connection is established. For each connection that occurs, the trace flag writes two entries that look like this:
Login: sa saSQL Query Analyzer(local)ODBCmaster, server process ID (SPID): 57, kernel process ID (KPID): 57.
Login: sa XANADUsaSQL Query Analyzer(local)ODBCmaster, server process ID (SPID): 57, kernel process ID (KPID): 57.
4022 If turns on, then automatically started procedures will be bypassed.
4029 Logs extended errors to errorlog when network disconnect occurs, turned off by default. Will dump out the socket error code this can sometimes give you a clue as to the root cause.
4030 Prints both a byte and ASCII representation of the receive buffer. Used when you want to see what queries a client is sending to SQL Server. You can use this trace flag if you experience a protection violation and want to determine which statement caused it. Typically, you can set this flag globally or use SQL Server Enterprise Manager. You can also use DBCC INPUTBUFFER.
4031 Prints both a byte and ASCII representation of the send buffers (what SQL Server sends back to the client). You can also use DBCC OUTPUTBUFFER.
4032 Traces the SQL commands coming in from the client. The output destination of the trace flag is controlled with the 3605/3604 trace flags.
4101 SQL 9 – Query that involves an outer join operation runs very slowly. However, if you use the FORCE ORDER query hint in the query, the query runs much faster. Additionally, the execution plan of the query contains the following text in theWarnings column:  NO JOIN PREDICATE
4121 Turn these trace flags after HOTFIX is applied (SP2 CUP4)
4606 Over comes SA password by startup. Refer to Ms article 936892.
4612 Disable the ring buffer logging – no new entries will be made into the ring buffer.
4613 Generate a minidump file whenever an entry is logged into the ring buffer.
4616 Makes server-level metadata visible to application roles. In SQL Server, 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 SQL Server. Setting this global flag disables the new restrictions, and allows for application roles to access server-level metadata. Scope: global only
5302 Alters default behavior of select…INTO (and other processes) that lock system tables for the duration of the transaction. This trace flag disables such locking during an implicit transaction.
6527 Disables generation of a memory dump on the first occurrence of an out-of-memory exception in CLR integration. By default, SQL Server 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:
·   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.
·   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. Scope: global only
7103 Disable table lock promotion for text columns. Refer to Ms article – 230044
7300 Retrieves extended information about any error you encounter when you execute a distributed query.
7501 Dynamic cursors are used by default on forward-only cursors. Dynamic cursors are faster than in earlier versions and no longer require unique indexes. This flag disables the dynamic cursor enhancements and reverts to version 6.0 behavior.
7502 Disables the caching of cursor plans for extended stored procedures.
7505 Enables version 6.x handling of return codes when calling dbcursorfetchex and the resulting cursor position follows the end of the cursor result set.
7525 Reverts to the SQL Server 7 behavior of closing nonstatic cursors regardless of the SET CURSOR_CLOSE_ON_COMMIT state in SQL Server 8.
7601 Turns on full text indexing. Together these four gather more information about full text search (indexing process) to the error log.
7646 SQL 10. Avoids blocking when using full text indexing. An issue we experienced that full text can be slow when there is a high number of updates to the index and is caused by blocking on the docidfilter internal table.
7806 Enables a dedicated administrator connection (DAC) on SQL Svr Express. By default, no DAC resources are reserved on SQL Server Express.
8004 SQL server to create a mini dump once you enable 2551 and a out of memory condition is hit.
8011 Disables the collection of additional diagnostic information for Resource Monitor. You can use the information in this ring buffer to diagnose out-of-memory conditions. Scope: GLOBAL.
8012 Records an event in the schedule ring buffer every time that one of the following events occurs:
·   A scheduler switches context to another worker.
·   A worker is suspended or resumed.
·   A worker enters the preemptive mode or the non-preemptive mode.
You can use the diagnostic information in this ring buffer to analyze scheduling problems. For example, you can use the information in this ring buffer to troubleshoot problems when SQL Server stops responding.
Trace flag 8012 disables recording of event

 

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