dbcc Trace

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mob604756fadec0 2012-05-11 14:01:00

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//z 2012-5-11 14:04:12 PM IS2120@CSDN

DBCC TRACEON - Enable trace flags.
DBCC TRACEOFF - Disable trace flags.
DBCC TRACESTATUS - Display the status of trace flags.

Syntax
      DBCC TRACEON ( trace# [ ,...n ][ , -1 ] ) [WITH NO_INFOMSGS]

      DBCC TRACEOFF ( trace# [ ,...n ] [ , -1 ] ) [WITH NO_INFOMSGS]

      DBCC TRACESTATUS ( [ [trace# [,...n ] ]  [,] [-1] ] ) [WITH NO_INFOMSGS]

 Key:

   trace#      - Number of the trace flag(s)
   -1          - Display the status of trace flags that are enabled globally.
   NO_INFOMSGS - Suppress all information messages.

By default all trace flags that are enabled for the session are displayed.

Examples

-- Turn flag on
DBCC TRACEON (3205)
GO
-- Turn flag on globally
DBCC TRACEON (2528, -1)
GO
-- Turn flag off
DBCC TRACEOFF (3205);
GO
-- Show flag status
DBCC TRACESTATUS (2528, 3205)
GO

//z 2012-5-11 14:04:12 PM IS2120@CSDN

Trace Flags

#	Flag
260	Print versioning information about extended stored procedure DLLs.	global or session
1204	Returns the resources and types of locks participating in a deadlock and also the current command affected.	global
1211	Disable all lock escalation. This trace flag may reduce performance. Takes precedence over flag 1224	global or session
1222	Return the resources,command and lock types that are participating in a deadlock (XML).	global
1224	Disable lock escalation based on the number of locks. Helps avoid "out-of-locks" errors when many locks are being used.	global
4616	Makes server-level metadata visible to application roles. i.e Revert to pre- SQL Server 2005 behavior.	global
2528	Disable parallel checking of objects by DBCC CHECK commands. Parallel DBCC should typically be left enabled.	global or session
3205	Disable hardware compression for tape drivers.	global or session
3625	Limit the amount of information returned in error messages.	global
7806	Enable a dedicated administrator connection (DAC) on SQL Server Express.	global

In order to see things printed to console, users would need to start up SQL Server from a command window with a -c argument. However, this is not what customer usually does. SQL Server provides another traceflag -T3605 which can be used to print console data to SQL Server errorlog file.

In this blog, I will introduce two useful traceflags related to TDS, -T4052/-T4055.-T4052 can be used to print the TDS packet sent to client (i.e. output) to console.-T4055 can be used to print the TDS packet received (i.e. input) to console.Both traceflag are startup only, meaning it can only be turned on during server startup. With these two traceflags, you can see everything that flows in and out of SQL Server.

You can search master.mdf HKLM\SOFTWARE\Wow6432Node\Microsoft\Microsoft SQL Server (remove Wow6432Node if 64-bit instance) to find the location for configuring startup parameters in SQL Server. The location is under:

HKLM\SOFTWARE\Wow6432Node\Microsoft\Microsoft SQL Server\<InstanceID>\MSSQLServer\Parameters

Add three string values under the key:

SQLArg3 --> -T4052
SQLArg4 --> -T4055
SQLArg5 --> -T3605

The number after SQLArg does not have to be 3/4/5. As long as it's unique, it's OK. Remember to update <InstanceID> with the instance ID of your own instance.

Now, restart your SQL Server, you will see all TDS data in SQL Server errorlog.

If you are using SQL Server 6.0, set trace flag 4032 to capture incoming SQL commands to the server. The following are two basic methods you can use to do this:

Start Sqlservr.exe with the command line parameters -T4032and -T3605.
Run dbcc traceon(-1, 3605, 4032) from Isqlw.exe or Isql.exeto set up capturing of SQL commands.

//z 2012-5-11 14:04:12 PM IS2120@CSDN

Trace flags can be used to alter SQL Server behavior temporarily. Trace flags can be turned on for a specific connection, or server-wide. Trace flags can be a great tool for troubleshooting a particular issue, however be forewarned: some trace flags are dangerous - use them at your own risk and be prepared to rebuild the server from scratch. Furthermore, functionality of certain trace flags might not be supported in future versions of SQL Server, so definitely avoid setting trace flags in your T-SQL code. We strongly recommend against using undocumented trace flags on production systems unless you're directed to do so by Microsoft's technical support.

To turn on a particular trace flag for a given connection, you execute the DBCC TRACEON command with the trace flag number specified in parenthesis, as follows:

1./* send the output of DBCC commands to the client */ DBCC TRACEON (3604)

To enable a trace flag on the SQL Server instance level you need to start SQL Server with the /T parameter followed by the trace flag number. If you start SQL Server with a trace flag, all connections will automatically have the same trace flag turned on. For example, to collect deadlock related information you could start the default instance of the SQL Server instance from the command prompt as follows:

1.NETSTART MSSQLSERVER /T1205

You can check the status of a particular trace flag by executing DBCC TRACESTATUS. Turn off a previously turned on trace flag using DBCC TRACEOFF. For example:

1.DBCCTRACESTATUS(3604) DBCC TRACEOFF(3604)

You can check all trace flags turned on for the current connection by passing -1 as the parameter of DBCC TRACESTATUS, for example:

1.DBCCTRACESTATUS(-1)

Results:

1.TraceFlag Status --------- ------

2520      
 1  3604       1

If you have no trace flags turned on, SQL Server will return the following message:

1.Traceoption(s)not enabled for

this

connection.Use 'DBCC TRACEON()'.

Next, we discuss some of the more frequently used trace flags. As mentioned above, some of these can be very powerful and therefore should be handled with care.

DBCC TRACEON / TRACEOFF (-1)

This flag advises SQL Server to turn on the trace flags turned on for the current connection on all subsequent client connections. For example, if you have turned on 3604 and 2520 on the current connection and you execute DBCC TRACEON(-1) all subsequent connections to the server will have 3604 and 2520 turned on. Similarly, if you wish to turn a particular trace flag for all connections simply execute it along with -1, as in DBCC TRACEON(-1, 3604). Executing DBCC TRACEOFF(-1) will automatically turn off all trace flags on the current and any subsequent connections. DBCC TRACEON (2528)

This flag disables parallelism during executing of maintenance DBCC statements, such as DBCC CHECKDB, DBCC CHECKFILEGROUP and DBCC CHECKTABLE. By default SQL Server will determine the needed degree of parallelism during query execution. Usually it is recommended to let SQL Server decide whether parallelism will be useful. Occasionally, if you only wish to use a single processor for DBCC statements, you might wish to override the default behavior. Remember that turning off parallelism might increase the total time required for executing DBCC commands. DBCC TRACEON(3604) and DBCC TRACEON(3605)

The first flag (3604) sends the output of (some) DBCC commands and trace flags to the Query Analyzer; 3605 sends the same output to SQL Server error log. For example, the following commands will generate a list of the 10 longest buffer chains in Query Analyzer:

1.DBCCTRACEON(3604) DBCC BUFCOUNT

Results:

1.****

THE
 10 LONGEST BUFFER CHAINS

****

bucket number

= 514 chain size =3 bucket number = 522 chain size

2 bucket number = 770 chain size

2 bucket number = 1026 chain size

2 bucket number = 269 chain size

1 bucket number = 272 chain size

1 bucket number = 274 chain size

1 bucket number = 281 chain size

1 bucket number = 283 chain size

1 bucket number = 284 chain size

1 The Smallest Chain Sizeis

: 0    The Average Chain

Size is: 0.005066

If you turn off 3604 and turn on 3605, instead you'll get the same result in the error log. You can double check this by executing the following:

1.EXECmaster..xp_readerrorlog

Abbreviated results:

1.

ERRORLOG                                                                        ContinuationRow  2003

-10-

24
 21:00:31.51 spid51       bucket number

=


514       chain

size =3 0 2003-10-

24 21:00:31.51 spid51      
 bucket number

=

522       chain

size=


2    0  2003

-10-24 21:00:31.51 spid51 bucket number= 770 chain size= 2 0 2003-10-24 21:00:31.51 spid51 bucket number= 1026 chain size= 2 0 2003-10-24 21:00:31.51 spid51 bucket number= 269 chain size= 1 0 2003-10-24 21:00:31.51 spid51 bucket number= 272 chain size= 1 0 2003-10-24 21:00:31.51 spid51 bucket number= 274 chain size= 1 0 2003-10-24 21:00:31.51 spid51 bucket number= 281 chain size= 1 0 2003-10-24 21:00:31.51 spid51 bucket number= 283 chain size= 1 0 2003-10-24 21:00:31.51 spid51 bucket number= 284 chain size= 1 0 2003-10-24 21:00:31.51 spid51 The Smallest ChainSize is: 0 0 2003-10-

24 21:00:31.51 spid51      The Average Chain

Size is: 0.005066 0

DBCC TRACEON(1204) , DBCC TRACEON(1205) and DBCC TRACEON(1206)

These trace flags are used to troubleshoot deadlocks. 1204 returns deadlock chains and the victim SPID. 1205 returns the details of the commands (stack traces) involved in the deadlock. Along with these flags you should also turn on 3605 to send the output of the trace to the SQL Server error log. 1206 can be used to supplement the information collected by the other two trace flags by returning all lock activities performed by deadlocked connections. The output of 1206 can be very large.

If you wish to see what deadlock output looks like, simply open two connections to the same SQL Server instance through Query Analyzer and execute following on one of them:

1.DBCCTRACEON(-

1,
 1204

) DBCC


TRACEON

(-1, 1205) DBCC TRACEON(-1, 3605)

Next execute the following on the first connection:

1.USE

pubs

BEGIN TRAN


UPDATE

titles SET title ='deadlock battle' WAITFORDELAY '00:00:05' UPDATE authors SET

address

= '110 north main'

At the same time execute the following script from the other connection:

1.USE

pubs

BEGIN TRANSACTION UPDATE authors SET address ='115 East 43rd street' UPDATEtitles SET title =


'who can win?'

One of these connections will be chosen as a deadlock victim and its transaction will be aborted by SQL Server. Now if you read the error log, you will find entries similar to the following:

1.spid4 ----------------------------------

spid4    
 Starting deadlock

search1 spid4 Target Resource Owner: spid4 ResType:LockOwner Stype:'OR'Mode: U SPID:53 ECID: Ec:(

x195
 756

) Value: x1916eb4 spid4 Node:1 ResType:LockOwner Stype:'OR'Mode: U SPID:53 ECID: Ec:(

x195
 756

) Value

: x1916eb4     spid4     spid4

Enddeadlock search 1 ... a deadlock was not


found

. spid4 ----------------------------------

spid4

----------------------------------

spid4    
 Starting deadlock

search2 spid4 Target Resource Owner: spid4 ResType:LockOwner Stype:'OR'Mode: U SPID:52 ECID: Ec:(

x1947756

) Value: x1916e72 spid4 Node:1 ResType:LockOwner Stype:'OR'Mode: U SPID:52 ECID: Ec:(

x1947756

) Value: x1916e72 spid4 Node:2 ResType:LockOwner Stype:'OR'Mode: U SPID:53 ECID: Ec:(

x195
 756

) Value

: x1916eb4     spid4

Cycle: ResType:LockOwner Stype:'OR'Mode: U SPID:52 ECID: Ec:(

x1947756

) Value: x1916e72 spid4 spid4 spid4 <

b>Deadlock

cycle

was encountered .... verifying

cycle spid4 Node:1 ResType:LockOwner Stype:'OR'Mode: U SPID:52 ECID: Ec:(

x1947756

) Value: x1916e72 Cost:(/

) spid4 Node:2 ResType:LockOwner Stype:'OR'Mode: U SPID:53 ECID: Ec:(

x195 756

) Value: x1916eb4 Cost:(/B88)

spid4

Cycle: ResType:LockOwner Stype:'OR'Mode: U SPID:52 ECID: Ec:(

x1947756

) Value: x1916e72 Cost:(/

) spid4 spid4 Deadlock encountered .... Printing deadlock information spid4 spid4 Wait-for graph spid4 spid4 Node:1 spid4 KEY: 5:1977 58 79:1( 1 1aedb232b)

CleanCnt:1 Mode: X Flags:  x    spid4

GrantList:: spid4 Owner: x1916ee2 Mode: X Flg: x Ref: Life: 2 SPID:53 ECID: spid4 SPID: 53 ECID: Statement Type: UPDATE

Line #: 1    spid4

InputBuf: Language Event: begintran update authors set address =


'115 East 43rd street '

update


titles

settitle = 'who can win?' spid4 RequestedBy: spid4 ResType:LockOwner Stype:'OR'

Mode:
 U SPID:52 ECID:  Ec:

(

x1947756

) Value: x1916e72 Cost:(/

)

spid4       spid4     Node:2     spid4

KEY: 5:2121 58592:1(a7 64fb1eac)

CleanCnt:1 Mode: X Flags:  x     spid4

GrantList:: spid4 Owner: x191813 Mode: X Flg: x Ref: Life: 2 SPID:52 ECID: spid4 SPID: 52 ECID: Statement Type: UPDATE

Line #: 1    spid4

InputBuf: Language Event: begintran update titles set title=' deadlock battle'' waitfor delay ' : : 5' update authors set address='

110
 north main

' spid4 Requested By: spid4 ResType:LockOwner Stype:'OR

' Mode: U SPID:53 ECID:  Ec:( x195 756 )                  Value: x1916eb4  Cost:(
 /B88)    spid4     Victim Resource Owner:     spid4      ResType:LockOwner Stype:'

OR

' Mode: U SPID:53 ECID:  Ec:( x195 756 )                Value: x1916eb4  Cost:( /B88)    spid4     spid4     <b>End
 deadlock search 2 ... a deadlock was found.</b>     spid4     ----------------------------------     spid4     ----------------------------------     spid4     Starting deadlock search 3    spid4     Target Resource Owner:     spid4      ResType:LockOwner
 Stype:'

OR

' Mode: U SPID:53 ECID:  Ec:( x195 756 )                Value: x1916eb4     spid4      Node:1  ResType:LockOwner Stype:'

OR

' Mode: U SPID:53
 ECID:  Ec:( x195 756 )                Value: x1916eb4     spid4      Node:2  ResType:LockOwner Stype:'

OR' Mode: U SPID:52 ECID: Ec:(

x1947756

) Value

: x1916e72     spid4     spid4

Previous victim encountered ... abortingsearch spid4 spid4 End deadlock search

3 ... a deadlock was

not found

.        spid4

----------------------------------

If you had also turned on trace flag 1206 you would get numerous messages similar to the following in the error log:

1.Process 52 acquiring IX lockon PAG: 5:1:99 (classbit2000000 ref1) result

: OK  Process 52 acquiring X lock

onKEY

: 5:2121058592:1

(b60057ff7752)(class bit2000000 ref1)


result

: OK Process 52 releasing lock referenceon KEY: 5:2121058592:2(9002e988d824)

Process 5 releasing

all locks @19116B3C

DBCC TRACEON(3205)

This flag disables hardware compression for tape drives. If the tape drive supports the compression, the BACKUP statement that backs up the database directly to tape will take advantage of hardware compression. If you must exchange tapes with another office where hardware compression is not supported, you might wish to turn on trace flag 3205 so that your tapes are compatible with the other office's hardware. DBCC TRACEON (4013)

This flag can be used to audit connections to the server. When turned on, the SQL Server error log will contain an entry for each successful connection. The log entry will look similar to the following:

1.Login: johndoe BP-

5CHSFFH2HEJ1johndoejohndoeSQL Query
 AnalyzerBP

-5CHSFFH2HEJ1ODBCmaster, server process ID(SPID): 55, kernel process ID(KPID)

:
 55.

As you might imagine the error log on a busy server will grow quite voluminous if this flag is turned on. DBCC TRACEON(4022)

This flag is used to bypass procedures marked for automatic execution at startup. Note that automatically executed procedures are also skipped if SQL Server is started with minimal configuration. DBCC TRACEON(2520)

This flag can be used to 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'".

DBCC TRACEON(2588)

This flag can be used to force DBCC HELP to return syntax of undocumented DBCC statements in SQL Server 2005 and 2008.

1.DBCC

TRACEON

(2588);DBCC

HELP

('?')GO DBCC TRACEOFF (2588);

DBCC TRACEON(1200)

This flag can be used to get a detailed report of all locks acquired by each SQL statement on the current connection - the output can be large depending on the number of rows involved. For example, take a look at the output of the following simple query:

1.SELECT

a.au_id, b.royaltyper

FROMauthors a INNER JOIN titleauthor b ON

a.au_id

= b.au_id ORDER BY2

Results (abbreviated):

1.Process 54 acquiringIS lock on

TAB: 5:53575229 []

(classbit0 ref1) result

: OK  Process 54 acquiring

ISlock on TAB: 5:1977058079 [] (classbit0 ref1) result

: OK  Process 54 acquiring

ISlock on PAG: 5:1:148 (classbit0 ref1) result

: OK  Process 54 acquiring