I'm collecting blocked process reports using Extended Events, and for some reason in some reports the blocking-process
node is empty. This is the full xml:
<blocked-process-report monitorLoop="383674">
<blocked-process>
<process id="processa7bd5b868" taskpriority="0" logused="106108620" waitresource="KEY: 6:72057613454278656 (8a2f7bc2cd41)" waittime="25343" ownerId="1051989016" transactionname="user_transaction" lasttranstarted="2017-03-20T09:30:38.657" XDES="0x21f382d9c8" lockMode="X" schedulerid="7" kpid="15316" status="suspended" spid="252" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2017-03-20T09:39:15.853" lastbatchcompleted="2017-03-20T09:39:15.850" lastattention="1900-01-01T00:00:00.850" clientapp="Microsoft Dynamics AX" hostname="***" hostpid="1348" loginname="***" isolationlevel="read committed (2)" xactid="1051989016" currentdb="6" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame line="1" stmtstart="40" sqlhandle="0x02000000f7def225b0edaecd8744b453ce09bdcff9b291f50000000000000000000000000000000000000000" />
<frame line="1" sqlhandle="0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000" />
</executionStack>
<inputbuf>
(@P1 bigint,@P2 int)DELETE FROM DIMENSIONFOCUSUNPROCESSEDTRANSACTIONS WHERE ((PARTITION=5637144576) AND ((FOCUSDIMENSIONHIERARCHY=@P1) AND (STATE=@P2))) </inputbuf>
</process>
</blocked-process>
<blocking-process>
<process />
</blocking-process>
</blocked-process-report>
The index definition for the index this hobt_id belongs to is
CREATE UNIQUE CLUSTERED INDEX [I_7402FOCUSDIMENSIONHIERARCHYIDX] ON [dbo].[DIMENSIONFOCUSUNPROCESSEDTRANSACTIONS]
(
[PARTITION] ASC,
[FOCUSDIMENSIONHIERARCHY] ASC,
[STATE] ASC,
[GENERALJOURNALENTRY] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
GO
There is no partitioning involved, this is the table definition:
CREATE TABLE [dbo].[DIMENSIONFOCUSUNPROCESSEDTRANSACTIONS](
[FOCUSDIMENSIONHIERARCHY] [bigint] NOT NULL DEFAULT ((0)),
[GENERALJOURNALENTRY] [bigint] NOT NULL DEFAULT ((0)),
[STATE] [int] NOT NULL DEFAULT ((0)),
[RECVERSION] [int] NOT NULL DEFAULT ((1)),
[PARTITION] [bigint] NOT NULL DEFAULT ((5637144576.)),
[RECID] [bigint] NOT NULL,
CONSTRAINT [I_7402RECID] PRIMARY KEY NONCLUSTERED
(
[RECID] ASC
)WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
) ON [PRIMARY]
GO
ALTER TABLE [dbo].[DIMENSIONFOCUSUNPROCESSEDTRANSACTIONS] WITH CHECK ADD CHECK (([RECID]<>(0)))
GO
There are no triggers or foreign keys defined on any of the tables in the entire database.
The exact SQL Server build is:
Microsoft SQL Server 2012 (SP3-CU4) (KB3165264) – 11.0.6540.0 (X64)
Jun 23 2016 17:45:11 Copyright (c) Microsoft Corporation Enterprise
Edition: Core-based Licensing (64-bit) on Windows NT 6.3 (Build
14393: ) (Hypervisor)
The extended events is fairly simple, just logging the blocked process reports:
CREATE EVENT SESSION [Dynperf_Blocking_Data] ON SERVER
ADD EVENT sqlserver.blocked_process_report(
ACTION(package0.collect_system_time,sqlserver.client_hostname,sqlserver.context_info)),
ADD EVENT sqlserver.lock_escalation(
ACTION(package0.collect_system_time,sqlserver.client_hostname,sqlserver.context_info)),
ADD EVENT sqlserver.xml_deadlock_report(
ACTION(package0.collect_system_time,sqlserver.client_hostname,sqlserver.context_info))
ADD TARGET package0.event_file(SET filename=N'F:\SQLTrace\Dynamics_Blocking.xel',max_file_size=(100),max_rollover_files=(10))
WITH (MAX_MEMORY=32768 KB,EVENT_RETENTION_MODE=ALLOW_SINGLE_EVENT_LOSS,MAX_DISPATCH_LATENCY=5 SECONDS,MAX_EVENT_SIZE=0 KB,MEMORY_PARTITION_MODE=PER_NODE,TRACK_CAUSALITY=ON,STARTUP_STATE=ON)
GO
The database is configured in Read Committed Snapshot Isolation, and max degree of parallelism is set to 1. This is the server configuration:
+------------------------------------+-------+
| name | value |
+------------------------------------+-------+
| access check cache bucket count | 0 |
| access check cache quota | 0 |
| Ad Hoc Distributed Queries | 0 |
| affinity I/O mask | 0 |
| affinity mask | 0 |
| affinity64 I/O mask | 0 |
| affinity64 mask | 0 |
| Agent XPs | 1 |
| allow updates | 0 |
| backup compression default | 1 |
| blocked process threshold (s) | 2 |
| c2 audit mode | 0 |
| clr enabled | 0 |
| common criteria compliance enabled | 0 |
| contained database authentication | 0 |
| cost threshold for parallelism | 5 |
| cross db ownership chaining | 0 |
| cursor threshold | -1 |
| Database Mail XPs | 1 |
| default full-text language | 1033 |
| default language | 0 |
| default trace enabled | 1 |
| disallow results from triggers | 0 |
| EKM provider enabled | 0 |
| filestream access level | 0 |
| fill factor (%) | 0 |
| ft crawl bandwidth (max) | 100 |
| ft crawl bandwidth (min) | 0 |
| ft notify bandwidth (max) | 100 |
| ft notify bandwidth (min) | 0 |
| index create memory (KB) | 0 |
| in-doubt xact resolution | 0 |
| lightweight pooling | 0 |
| locks | 0 |
| max degree of parallelism | 1 |
| max full-text crawl range | 4 |
| max server memory (MB) | 65536 |
| max text repl size (B) | 65536 |
| max worker threads | 0 |
| media retention | 0 |
| min memory per query (KB) | 1024 |
| min server memory (MB) | 0 |
| nested triggers | 1 |
| network packet size (B) | 4096 |
| Ole Automation Procedures | 0 |
| open objects | 0 |
| optimize for ad hoc workloads | 1 |
| PH timeout (s) | 60 |
| precompute rank | 0 |
| priority boost | 0 |
| query governor cost limit | 0 |
| query wait (s) | -1 |
| recovery interval (min) | 0 |
| remote access | 1 |
| remote admin connections | 0 |
| remote login timeout (s) | 10 |
| remote proc trans | 0 |
| remote query timeout (s) | 600 |
| Replication XPs | 0 |
| scan for startup procs | 1 |
| server trigger recursion | 1 |
| set working set size | 0 |
| show advanced options | 1 |
| SMO and DMO XPs | 1 |
| transform noise words | 0 |
| two digit year cutoff | 2049 |
| user connections | 0 |
| user options | 0 |
| xp_cmdshell | 0 |
+------------------------------------+-------+
I ran a server side trace for a while and I get the same empty nodes in a trace file as I do using extended events.
This blocked process report was captured using a server side trace on another server also running Dynamics AX, so it's not specific to this server or build.
<blocked-process-report monitorLoop="1327922">
<blocked-process>
<process id="processbd9839848" taskpriority="0" logused="1044668" waitresource="KEY: 5:72057597098328064 (1d7966fe609a)" waittime="316928" ownerId="3415555263" transactionname="user_transaction" lasttranstarted="2017-03-27T07:59:29.290" XDES="0x1c1c0c3b0" lockMode="U" schedulerid="3" kpid="25236" status="suspended" spid="165" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2017-03-27T07:59:47.873" lastbatchcompleted="2017-03-27T07:59:47.873" lastattention="2017-03-27T07:58:01.490" clientapp="Microsoft Dynamics AX" hostname="***" hostpid="11072" loginname="***" isolationlevel="read committed (2)" xactid="3415555263" currentdb="5" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame line="1" stmtstart="236" stmtend="676" sqlhandle="0x020000004d6830193d42a167edd195c201f40bb772e9ece20000000000000000000000000000000000000000"/>
</executionStack>
<inputbuf>
(@P1 numeric(32,16),@P2 int,@P3 bigint,@P4 nvarchar(5),@P5 nvarchar(36),@P6 int,@P7 numeric(32,16),@P8 bigint,@P9 int)UPDATE PRODCALCTRANS SET REALCOSTAMOUNT=@P1,RECVERSION=@P2 WHERE (((((((PARTITION=@P3) AND (DATAAREAID=@P4)) AND (COLLECTREFPRODID=@P5)) AND (COLLECTREFLEVEL=@P6)) AND (LINENUM=@P7)) AND (RECID=@P8)) AND (RECVERSION=@P9)) </inputbuf>
</process>
</blocked-process>
<blocking-process>
<process/>
</blocking-process>
</blocked-process-report>
Does anybody have an explanation for these reports? What is blocking the query?
Is there any way to find out what was happening if I'm looking at the reports after the locks have long gone?
One thing that might be useful to add is that these queries are run via sp_cursorprepare
and sp_cursorexecute
So far I haven't been able to reproduce it, it seems to happen randomly but very often.
It happens on several instances (of different builds) and several tables/queries, all related to Dynamics AX.
There are no index or other database maintenance jobs occurring in the background at the time.
Using the code provided in the answer by srutzky I was able to capture some logging related to this blocked process report:
<blocked-process-report monitorLoop="1621637">
<blocked-process>
<process id="processd06909c28" taskpriority="0" logused="0" waitresource="KEY: 5:72057597585719296 (d2d87c26d920)" waittime="78785" ownerId="4436575948" transactionname="user_transaction" lasttranstarted="2017-04-13T07:39:17.590" XDES="0x3219d034e0" lockMode="U" schedulerid="3" kpid="133792" status="suspended" spid="106" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2017-04-13T07:39:17.657" lastbatchcompleted="2017-04-13T07:39:17.657" lastattention="1900-01-01T00:00:00.657" clientapp="Microsoft Dynamics AX" hostname="****" hostpid="11800" loginname="****" isolationlevel="read committed (2)" xactid="4436575948" currentdb="5" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame line="1" stmtstart="72" stmtend="256" sqlhandle="0x0200000076a6a92ab1256af09321b056ab243f187342f9960000000000000000000000000000000000000000"/>
<frame line="1" sqlhandle="0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"/>
</executionStack>
<inputbuf>
(@P1 int,@P2 int,@P3 bigint,@P4 int)UPDATE PRODROUTEJOB SET JOBSTATUS=@P1,RECVERSION=@P2 WHERE ((RECID=@P3) AND (RECVERSION=@P4)) </inputbuf>
</process>
</blocked-process>
<blocking-process>
<process/>
</blocking-process>
</blocked-process-report>
This is found in the logging tables for the same resource around that time: Gist because of character limit
Further investigation shows that just before and after the report with an empty blocking process I have reports for the same resourceid that do have blocking process nodes:
<blocked-process-report monitorLoop="1621636">
<blocked-process>
<process id="processd06909c28" taskpriority="0" logused="0" waitresource="KEY: 5:72057597585719296 (d2d87c26d920)" waittime="73765" ownerId="4436575948" transactionname="user_transaction" lasttranstarted="2017-04-13T07:39:17.590" XDES="0x3219d034e0" lockMode="U" schedulerid="3" kpid="133792" status="suspended" spid="106" sbid="0" ecid="0" priority="0" trancount="2" lastbatchstarted="2017-04-13T07:39:17.657" lastbatchcompleted="2017-04-13T07:39:17.657" lastattention="1900-01-01T00:00:00.657" clientapp="Microsoft Dynamics AX" hostname="***" hostpid="11800" loginname="***" isolationlevel="read committed (2)" xactid="4436575948" currentdb="5" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack>
<frame line="1" stmtstart="72" stmtend="256" sqlhandle="0x0200000076a6a92ab1256af09321b056ab243f187342f9960000000000000000000000000000000000000000"/>
<frame line="1" sqlhandle="0x0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"/>
</executionStack>
<inputbuf>
(@P1 int,@P2 int,@P3 bigint,@P4 int)UPDATE PRODROUTEJOB SET JOBSTATUS=@P1,RECVERSION=@P2 WHERE ((RECID=@P3) AND (RECVERSION=@P4)) </inputbuf>
</process>
</blocked-process>
<blocking-process>
<process status="sleeping" spid="105" sbid="0" ecid="0" priority="0" trancount="1" lastbatchstarted="2017-04-13T07:40:31.417" lastbatchcompleted="2017-04-13T07:40:31.423" lastattention="1900-01-01T00:00:00.423" clientapp="Microsoft Dynamics AX" hostname="**" hostpid="11800" loginname="**" isolationlevel="read committed (2)" xactid="4436165115" currentdb="5" lockTimeout="4294967295" clientoption1="671088672" clientoption2="128056">
<executionStack/>
<inputbuf>
(@P1 bigint,@P2 nvarchar(5),@P3 bigint,@P4 bigint,@P5 nvarchar(11),@P6 int,@P7 nvarchar(21),@P8 datetime2)SELECT T1.REGDATETIME,T1.REGDATETIMETZID,T1.WORKERPILOT,T1.WORKER,T1.WRKCTRIDPILOT,T1.REGTYPE,T1.PROFILEDATE,T1.JOBID,T1.JOBIDABS,T1.MATCHRECIDSTARTSTOP,T1.JOBACTIVE,T1.RESNO,T1.STARTITEMS,T1.GOODITEMS,T1.SCRAPITEMS,T1.FINISHEDCODE,T1.TMPGOODITEMS,T1.TMPSCRAPITEMS,T1.SYSMRPUPDATEREQUEST,T1.ERROR,T1.ERRORTXT,T1.TMPSTARTITEMS,T1.AUTOSTAMP,T1.ERRORSPECIFICATION,T1.COSTCATEGORY,T1.ONCALLACTIVITY,T1.TERMINALID,T1.PDSCWGOODITEMS,T1.PDSCWSCRAPITEMS,T1.PDSCWSTARTITEMS,T1.RETAILTERMINALID,T1.MODIFIEDDATETIME,T1.RECVERSION,T1.PARTITION,T1.RECID FROM JMGTERMREG T1 WHERE (((PARTITION=@P1) AND (DATAAREAID=@P2)) AND (((((WORKER=@P3) OR ((WORKER=@P4) AND (WRKCTRIDPILOT=@P5))) AND (REGTYPE=@P6)) AND (JOBID=@P7)) AND (REGDATETIME>=@P8))) ORDER BY T1.REGDATETIME </inputbuf>
</process>
</blocking-process>
</blocked-process-report>
Using the new script provided by srutzky new data has been collected.
It's posted on github because of the maximum post length.
Since the originally posted data didn't have both session id's some new data has been posted on github again
New data including the connections on github
Best Answer
I can't test this theory at the moment, but based on the most recent capture data posted to GitHub, I would say that the reason that thee
<process>
node is empty is that it requires a currently running request (many of the attributes are found insys.dm_exec_requests
and not insys.dm_exec_sessions
) and without a currently running request, it can't report any details, similar to how doing anINNER JOIN
betweensys.dm_exec_requests
andsys.dm_exec_sessions
will exclude rows where a Session is active but is idle due to no current request.Looking at the top set of data (
monitorLoop
values: 1748823, 1748824, 1748825, and 1748827) we can see the following:id
of theblocked-process
is the same in each case: process2552c1fc28, and the only attribute that is different is thewaittime
(understandably).blocking-process
nodes show differences in bothlastbatchstarted
andlastbatchcompleted
blocking-process
nodes show identical values forspid
andxactid
So, how can the SessionID and TransactionID of the blocking process be the same across 4 different query batches? Easy, an explicit transaction was started and then these batches were executed. And because these are seperate batches, there is time between them being submitted, at which point there is no current request, hence no process info to show (but the session and the transaction are still there).
In order to do additional research into this, you can capture helpful information from
sys.dm_exec_requests
andsys.dm_tran_locks
by placing the following T-SQL in a SQL Server Agent "Transaction-SQL script (T-SQL)" Job Step, setting the "Database" to be the one you are researching (in this case it is the one with an ID of 6), and scheduling this job to run every 10 seconds. The T-SQL below will create the two tables in that same DB if they don't exist and then will populate the "Requests" table if any request is either blocking itself, or if it is a Delete or Update operation that is being blocked. If any requests are found, it will try to capture:RIGHT JOIN
to at least get the Session info)the current locks for those same session_id's (just keep in mind that the lock info isn't guaranteed to be 100% accurate as that info can change in the time between those two statements executing; still, the info is good enough often enough to be worth capturing).This section is currently commented out.SQL Server Agent T-SQL Job Step:
I think you should be able to reproduce this by opening one query tab and executing the following:
Then, open a second query tab and execute the following:
P.S. Just to have it stated, the only thing that does not make sense is that the request & session info –
dbo.tmpBlockingResearch_Requests
– still never contains rows for the blocking session. Yet I know that the table variable has the blocking session id in it as it did pull in the locks for both SessionIDs. This could point to a scenario in which a Transaction is allowed to stay open after the "connection" from the client is closed but the connection is still maintained due to Connection Pooling.