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• How to manually detect deadlocks

  - by Dawson

  I understand the concepts of deadlock well enough, but when I'm given a problem like the one below I'm not sure how to go about solving it. I can draw a resource allocation graph, but I'm not sure how to solve it from there. Is there a better more formal way of solving this? Consider a system with five processes, P1 through P5, and five resources, R1 through R5. Resource ownership is as follows. • P1 holds R1 and wants R3 • P2 holds R2 and wants R1 • P3 holds R3 and wants R5 • P4 holds R5 and wants R2 • P5 holds R4 and wants R2 Is this system deadlocked? Justify your answer. If the system is deadlocked, list the involved processes.

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• svn-based versioning tool, problem with network timeout

  - by Scarlet

  My dev team was committed a versioning tool based on Subversion to run on Windows (our svn client is sliksvn). We're developing with Delphi XE2, should that matter. We're asked to implement a "check for updates availability" feature, which has to work as follows: Connect to the SVN repo via svn+ssh protocol; See if there are changes to receive and list them; Let the user decide if he wants to receive changes or not. We don't have a great knowledge on svn, so we thought to implement that thing client side by a certain number of CreateProcess calls that wrap directly proper svn commands. Anyways what we perceived is that if network problems should arise, such like a connection drop, svn client hangs forever waiting for the operation to close instead of failing for timeout. We know that CreateProcess can be given a timeout argument, but it wouldn't be correct to use it, as we can't know from outside how long will be the svn operation taking to complete. Is there any way to avoid that deadlock?

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• Redefinition Error

  - by ahmed-zeb

  I am converting an MFC application for deadlock detection in to Simple console application. During this process I found many errors saying like error C2365: 'CmdLockMutex' : redefinition; previous definition was 'enumerator' I am unable to remove this error. Kindly if someone could help me in this regard.

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• BerkeleyDB vs. Tokyo Cabinet

  - by vsedach

  I'm looking for general experiences from people who have used both, particularly on how the two compare on handling large numbers of records, transaction/concurrency/deadlock handling, and juicy stories about database corruption and backup procedures.

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• R adding infrequent date 'events' to a time series plot

  - by flyingcrab

  Hi, I am just starting on R - and have hit a bit of a deadlock with some time series data. I have a time series (date and value) in 'zoo' format, that I want to annotate with a cross when an event occurs. The events are irregular and in a csv format (just the dates, sometimes repeated). I've managed to read in the dates etc into a format that R accepts - but i cant seem to get a means to chart the main time series with the secondary events annotated on top?

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• accessing one text

  - by dev1

  ASp.NET application. In button click i am accessing one text file and reading content. while both users clicking this button at a time deadlock will occurs so how to handle this i want to read each user one by one can any one suggest method to handle. i am looking to handle with waithandle events so can any one give a code sample for above scenario.

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• Detecting a stale Mutex

  - by sum1stolemyname

  Is there any technique or tool available to detect this kind of a deadlock during runtime? picture this in a worker thread (one of several, normally 4-6) try WaitForSingleObject(myMutex); DoSTuffThatMightCauseAnException; Except ReleaseMutex(myMutex); end; or more generally is there a design-pattern to avoid these kind of bugs? I coded the above code in the little hous after a longer hacking run

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• How can I set a breakpoint on _NSLockError()

  - by Sheehan Alam

  I am trying to debug multiple threads. *** -[NSLock lock]: deadlock (<NSLock: 0xc388ab0> '(null)') *** Break on _NSLockError() to debug. How can I debug this?

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• Some questions regarding threads and deadlocks

  - by mousey

  will parent process and child process in deadlock if parent is using resource and child will also get same resource ? what if parent contains two threads ? will child also get 2 threads ? how can fork will be thread safe ?

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• deadlocked on lock | communication buffer resources

  - by Robert Wilkinson

  Do all deadlocks indicate a problem with the query or does this kind deadlock indicate a problem with something else like SQL mail or something? The stored proc in question uses SQL mail.

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• Adding a clustered index to a SQL table: what dangers exist for a live production system?

  - by MoSlo

  Right, keep in mind i need to describe this by abstracting all possible confidential info: I've been put in charge of a 10-year old transactional system of which the majority business logic is implemented at database level (triggers, stored procedures etc). Win2000 server, MSSQL 2000 Enterprise. No immediate plans for replacing/updating the system are being considered :( The core process is a program that executes transactions - specifically, it executes a stored procedure with various parameters, lets call it sp_ProcessTrans. The program executes the stored procedure at asynchronous intervals. By itself, things work fine. But there are 30 instances of this program on remotely located workstations, all of them asynchronously executing sp_ProcessTrans and then retrieving data from the SQL server (execution is pretty regular - ranging 0 to 60 times a minute, depending on what items the program instance is responsible for) . Performance of the system has dropped considerably with 10 yrs of data growth: the reason is the deadlocks and specifically deadlock wait times. The deadlock is on the Employee table. I have discovered: In sp_ProcessTrans' execution, it selects from an Employee table 7 times (dont ask) The select is done on a field that is NOT the primary key No index exists on this field. Thus a table scan is performed. 7 times. per transaction So the reason for deadlocks is clear. I created a non-unique ordered clustered index on the field (field looks good, almost unique, NUM(7), very rarely changes). Immediate improvement in the test environment. The problem is that i cannot simulate the deadlocks in a test environment (I'd need 30 workstations; i'd need to simulate 'realistic' activity on those stations, so visualization is out). I need to know if i must schedule downtime. Creating an index shouldn't be a risky operation for MSSQL, but is there any danger (data corruption in transactions/select statements/extra wait time etc) to create this field index on the production database while the transactions are still taking place? (although i can select a time when transactions are fairly quiet through the 30 stations) Are there any hidden dangers i'm not seeing (not looking forward to needing to restore the DB if something goes wrong, restoring would take a lot of time with 10yrs of data).

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• sqlserver how to set job priority

  - by Buzz

  Is there any way to set one job priority higher then other, In my case there are two jobs those are working on same set of tables,first JOB-A which is running every 12 hr and other JOB-B is every 10 minutes , i think at some time when they run simultaneously JOB-B is getting in to deadlock and get failed, i google the topic and found sqlgoverner is helpful in such cases does anyone know how to resolve?

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• Getting the process id of a current process without unistd.h

  - by syaoran

  I'm working on a deadlock detection algorithm and I'm only given kernel level libraries, i.e. #include <linux/somelibrary> and nothing else. Are there kernel-level facilities that will allow me to get the pid of the current process similar to getpid() of unistd.h?

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• reading txt storing in different

  - by dev2

  ASp.NET application. In button click i am accessing one text file and reading content and storing in other destination. while both users clicking this button at a time deadlock(thread is being used by other process) will occurs so how to handle this i want to read each user one by one can any one suggest method to handle. i am looking to handle with waithandle events so can any one give a code sample for above scenario.

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• How do I read and write to a file using threads in java?

  - by WarmWaffles

  I'm writing an application where I need to read blocks in from a single file, each block is roughly 512 bytes. I am also needing to write blocks simultaneously. One of the ideas I had was BlockReader implements Runnable and BlockWriter implements Runnable and BlockManager manages both the reader and writer. The problem that I am seeing with most examples that I have found was locking problems and potential deadlock situations. Any ideas how to implement this?

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• Know More About Oracle Row Lock

  - by Liu Maclean(???)

  ??????Oracle??????????row lock,??ORACLE????????????????????,row lock???????????????????????????????,??Server Process?pin????block buffer????????? ????????,?process A ??update???????? Z?????????, ???????rollback???commit;??Process B??????DML??, ???????rowid???? Z???, ???????????process A????????ITL???,????????cleanout??,????????row???????????commit, ???????Process B????”enq: TX – row lock contention”??????? ????Process B????????????? ?????????Process A???????row,??Process B???????”enq: TX – row lock contention”???? ????????  ????????: SESSION A: SQL> select * from v$version; BANNER ---------------------------------------------------------------- Oracle Database 10g Enterprise Edition Release 10.2.0.5.0 - 64bi PL/SQL Release 10.2.0.5.0 - Production CORE    10.2.0.5.0      Production TNS for Linux: Version 10.2.0.5.0 - Production NLSRTL Version 10.2.0.5.0 - Production SQL> select * from global_name; GLOBAL_NAME -------------------------------------------------------------------------------- www.oracledatabase12g.com SQL> create table maclean_lock(t1 int); Table created. SQL> insert into maclean_lock values (1); 1 row created. SQL> commit; Commit complete. SQL> select dbms_rowid.rowid_block_number(rowid),dbms_rowid.rowid_relative_fno(rowid) from maclean_lock; DBMS_ROWID.ROWID_BLOCK_NUMBER(ROWID) DBMS_ROWID.ROWID_RELATIVE_FNO(ROWID) ------------------------------------ ------------------------------------                                67642                                    1 SQL>  select distinct sid from v$mystat;        SID ----------        142 SQL> select pid,spid from v$process where addr = ( select paddr from v$session where sid=(select distinct sid from v$mystat));        PID SPID ---------- ------------         17 15636 ??SESSION A ????savepoint ,?update ?????????         SQL>  savepoint NONLOCK; Savepoint created. SQL> select * From v$Lock where sid=142; no rows selected SQL> set linesize 140 pagesize 1400 SQL>  update maclean_lock set t1=t1+2; 1 row updated. SQL> select * From v$Lock where sid=142; ADDR             KADDR                   SID TY        ID1        ID2      LMODE    REQUEST      CTIME      BLOCK ---------------- ---------------- ---------- -- ---------- ---------- ---------- ---------- ---------- ---------- 0000000091FC69F0 0000000091FC6A18        142 TM      55829          0          3          0          6          0 00000000914B4008 00000000914B4040        142 TX     393232        609          6          0          6          0         SQL> select dump(3,16) from dual; DUMP(3,16) -------------------------------------------------------------------------------- Typ=2 Len=2: c1,4 ALTER SYSTEM DUMP DATAFILE 1 BLOCK 67642;  Object id on Block? Y  seg/obj: 0xda16  csc: 0x00.234718  itc: 2  flg: O  typ: 1 - DATA      fsl: 0  fnx: 0x0 ver: 0x01  Itl           Xid                  Uba         Flag  Lck        Scn/Fsc 0x01   0x000a.00f.000001e0  0x00800075.02a6.29  C---    0  scn 0x0000.00234711 0x02   0x0007.018.000001fe  0x0080065c.017a.02  ----    1  fsc 0x0000.00000000 data_block_dump,data header at 0x81d185c =============== tsiz: 0x1fa0 hsiz: 0x14 pbl: 0x081d185c bdba: 0x0041083a      76543210 flag=-------- ntab=1 nrow=1 frre=-1 fsbo=0x14 fseo=0x1f9a avsp=0x1f83 tosp=0x1f83 0xe:pti[0]      nrow=1  offs=0 0x12:pri[0]     offs=0x1f9a block_row_dump: tab 0, row 0, @0x1f9a tl: 6 fb: --H-FL-- lb: 0x2  cc: 1 col  0: [ 2]  c1 04 end_of_block_dump ?? BLOCK DUMP ???? ??????XID=0x0007.018.000001fe ?transaction?? lb:0x1 ??SESSION B ,?????UPDATE?? ???enq: TX - row lock contention ?? SQL> select distinct sid from v$mystat;        SID ----------        140 SQL> select pid,spid from v$process where addr = ( select paddr from v$session where sid=(select distinct sid from v$mystat));        PID SPID ---------- ------------         24 15652 SQL> alter system set "_trace_events"='10000-10999:255:24'; System altered.         SQL> update maclean_lock set t1=t1+2; select * From v$Lock where sid=142 or sid=140 order by sid; SESSION C: SQL> select * From v$Lock where sid=142 or sid=140 order by sid; ADDR             KADDR                   SID TY        ID1        ID2      LMODE    REQUEST      CTIME      BLOCK ---------------- ---------------- ---------- -- ---------- ---------- ---------- ---------- ---------- ---------- 0000000091FC6B10 0000000091FC6B38        140 TM      55829          0          3          0         84          0 00000000924F4A58 00000000924F4A78        140 TX     458776        510          0          6         84          0 00000000914B51E8 00000000914B5220        142 TX     458776        510          6          0        312          1 0000000091FC69F0 0000000091FC6A18        142 TM      55829          0          3          0        312          0 ???? SESSION B SID=140 ?SESSION A ?TX ENQUEUE ?X mode?REQUEST SQL> oradebug dump systemstate 266; Statement processed. SESSION B waiter's enqueue lock       SO: 0x924f4a58, type: 5, owner: 0x92bb8dc8, flag: INIT/-/-/0x00       (enqueue) TX-00070018-000001FE    DID: 0001-0018-00000022       lv: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  res_flag: 0x6       req: X, lock_flag: 0x0, lock: 0x924f4a78, res: 0x925617c0       own: 0x92b76be0, sess: 0x92b76be0, proc: 0x92a737a0, prv: 0x925617e0 TX-00070018-000001FE=> TX 458776 510 SESSION A owner's enqueue lock       SO: 0x914b51e8, type: 40, owner: 0x92b796d0, flag: INIT/-/-/0x00       (trans) flg = 0x1e03, flg2 = 0xc0000, prx = 0x0, ros = 2147483647 bsn = 0xed5 bndsn = 0xee7 spn = 0xef7       efd = 3       file:xct.c lineno:1179       DID: 0001-0011-000000C2       parent xid: 0x0000.000.00000000       env: (scn: 0x0000.00234718  xid: 0x0007.018.000001fe  uba: 0x0080065c.017a.02  statement num=0  parent xid: xid: 0x0000.000.00000000  scn: 0x00 00.00234718 0sch: scn: 0x0000.00000000)       cev: (spc = 7818  arsp = 914e8310  ubk tsn: 1 rdba: 0x0080065c  useg tsn: 1 rdba: 0x00800069             hwm uba: 0x0080065c.017a.02  col uba: 0x00000000.0000.00             num bl: 1 bk list: 0x91435070)             cr opc: 0x0 spc: 7818 uba: 0x0080065c.017a.02       (enqueue) TX-00070018-000001FE    DID: 0001-0011-000000C2       lv: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  res_flag: 0x6       mode: X, lock_flag: 0x0, lock: 0x914b5220, res: 0x925617c0       own: 0x92b796d0, sess: 0x92b796d0, proc: 0x92a6ffd8, prv: 0x925617d0        xga: 0x8b7c6d40, heap: UGA       Trans IMU st: 2 Pool index 65535, Redo pool 0x914b58d0, Undo pool 0x914b59b8       Redo pool range [0x86de640 0x86de640 0x86e0e40]       Undo pool range [0x86dbe40 0x86dbe40 0x86de640]         ----------------------------------------         SO: 0x91435070, type: 39, owner: 0x914b51e8, flag: -/-/-/0x00         (List of Blocks) next index = 1         index   itli   buffer hint   rdba       savepoint         -----------------------------------------------------------             0      2   0x647f1fc8    0x41083a     0xee7 ?SESSION A? ROLLBACK ?savepoint: SQL> rollback to NONLOCK; Rollback complete. ????savepoint ??update??????? ??UPDATE???????? ROLLBACK: SQL> select * From v$Lock where sid=142 or sid=140; ADDR             KADDR                   SID TY        ID1        ID2      LMODE    REQUEST      CTIME      BLOCK ---------------- ---------------- ---------- -- ---------- ---------- ---------- ---------- ---------- ---------- 00000000924F4A58 00000000924F4A78        140 TX     458776        510          0          6        822          0 0000000091FC6B10 0000000091FC6B38        140 TM      55829          0          3          0        822          0 00000000914B51E8 00000000914B5220        142 TX     458776        510          6          0       1050          1 ???? SESSION A 142 ???SAVEPOINT ???????TM LOCK ????? ROLLBACK TO SAVEPOINT?????SESSION???TX LOCK!!!! ??????SESSION 142???TX ID1=458776 ID2=510, ????ROLLBACK TO SAVEPOINT?????????ABORT TRANSACTION ?? SESSION B  SID=140??  SESSION A ?? , ?????????SESSION B? update???HANG?? ?????????CACHE?????:  Object id on Block? Y  seg/obj: 0xda16  csc: 0x00.2347b7  itc: 2  flg: O  typ: 1 - DATA      fsl: 0  fnx: 0x0 ver: 0x01  Itl           Xid                  Uba         Flag  Lck        Scn/Fsc 0x01   0x000a.00f.000001e0  0x00800075.02a6.29  C---    0  scn 0x0000.00234711 0x02   0x0000.000.00000000  0x00000000.0000.00  ----    0  fsc 0x0000.00000000 data_block_dump,data header at 0x745d85c =============== tsiz: 0x1fa0 hsiz: 0x14 pbl: 0x0745d85c bdba: 0x0041083a      76543210 flag=-------- ntab=1 nrow=1 frre=-1 fsbo=0x14 fseo=0x1f9a avsp=0x1f83 tosp=0x1f83 0xe:pti[0]      nrow=1  offs=0 0x12:pri[0]     offs=0x1f9a block_row_dump: tab 0, row 0, @0x1f9a tl: 6 fb: --H-FL-- lb: 0x0  cc: 1 col  0: [ 2]  c1 02 end_of_block_dump ???? ITL=0x02? ?????????,col  0: [ 2]  c1 02 ????????? ?????????SESSION D ,??????row lock?? ?UPDATE???????? SESSION D: SQL> update maclean_lock set t1=t1+2; 1 row updated. SQL> rollback; Rollback complete. ??SESSION B ??????????? ?????ORACLE????????, ??????????? TX lock?? row lock , ????????2??? row lock?????????, ?TX lock????????ENQUEUE LOCK???? ?????????PROCESS K?DML???????????????????????,??????????TX LOCK, ????PROCESS Z?????????????????????????ROW LOCK????????, ???????OLTP?????????????????????? ??ROW LOCK?Release ??????TX?ENQUEUE LOCK,?????????Process J ????????????, Process K??????????? ,Process K?????????,???row piece?lb??0x0 ,?????ITL, Process Z???ITL???????Process J????XID,?????Process J?????TX lock, PROCESS K ???TX resource?Enqueue Waiter Linked List?????X mode(exclusive)?enqueue lock? ???Process J??TX lock?,Process J?????TX resource?Enqueue Waiter Linked List ???Process K??????,??POST?????Process K? TX lock??????, ???????row lock???????,????????? ?????????? ?????: SESSION A ???PID =17 ?????????????????? SESSION B ???PID =24 ??????? "_trace_events"='10000-10999:255:24';  KST trace ??????? Server Process??? SESSION A PID=17  ?? acqure?SX mode???TM Lock ,?? ????Transaction?????UNDO SEGMENT 7,???XID 7.24.510, ?acquire ?X mode? TX-00070018-000001fe ? ?????? 00070018-000001fe ???? 7- 24 - 510? XID ? 781F4B8A:007A569C    17   142 10704  83 ksqgtl: acquire TM-0000da15-00000000 mode=SX flags=GLOBAL|XACT why="contention" 781F4B92:007A569D    17   142 10704  19 ksqgtl: SUCCESS 781F4BB3:007A569E    17   142 10812   2 0x000000000041083A 0x0000000000000000 0x0000000000234717 781F4BBA:007A569F    17   142 10812   3 0x0000000000000000 0x0000000000000000 0x0000000000000000 781F4BC0:007A56A0    17   142 10812   4 0x0000000000000000 0x0000000000000000 0x0000000000000000 781F4BD3:007A56A1    17   142 10812   5 0x000000000041083A 0x0000000000000000 0x0000000000000000 781F4BFE:007A56A2    17   142 10811   1 0x000000000041083A 0x0000000000000000 0x0000000000234711 0x0000000000000002 781F4C06:007A56A3    17   142 10811   2 0x000000000041083A 0x0000000000000000 0x0000000000234718 0x00007FA074EDA560 781F4C26:007A56A4    17   142 10813   1 ktubnd: Bind usn 7 nax 1 nbx 0 lng 0 par 0 781F4C43:007A56A5    17   142 10813   2 ktubnd: Txn Bound xid: 7.24.510 781F4C4A:007A56A6    17   142 10704  83 ksqgtl: acquire TX-00070018-000001fe mode=X flags=GLOBAL|XACT why="contention" 781F4C51:007A56A7    17   142 10704  19 ksqgtl: SUCCESS ?????????? ???????? 781F4CBF:007A56A8    17   142 10005   1 KSL WAIT BEG [SQL*Net message to client] 1650815232/0x62657100 1/0x1 0/0x0 781F4CCC:007A56A9    17   142 10005   2 KSL WAIT END [SQL*Net message to client] 1650815232/0x62657100 1/0x1 0/0x0 time=13 781F4CDE:007A56AA    17   142 10005   1 KSL WAIT BEG [SQL*Net message from client] 1650815232/0x62657100 1/0x1 0/0x0 786BD85D:007A57E0    17   142 10005   2 KSL WAIT END [SQL*Net message from client] 1650815232/0x62657100 1/0x1 0/0x0 time=5016447 786BD966:007A57E1    17   142 10005   1 KSL WAIT BEG [SQL*Net message to client] 1650815232/0x62657100 1/0x1 0/0x0 786BD96E:007A57E2    17   142 10005   2 KSL WAIT END [SQL*Net message to client] 1650815232/0x62657100 1/0x1 0/0x0 time=8 SESSION B ???PID =24  ,??????? SX mode? TM lock,??row lock? acquire X mode?TX-00070018-000001fe ksqgtl: acquire TM-0000da15-00000000 mode=SX flags=GLOBAL|XACT why="contention" ksqgtl: SUCCESS 0x000000000041083A 0x0000000000000000 0x00000000002354F8 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x0000000000000000 0x000000000041083A 0x0000000000000000 0x00000000002354F8 0x0000000000000001 0x000000000041083A 0x0000000000000000 0x00000000002354F8 0x0000000008A63780 0x0000000000000001 0x0000000000800861 0x0000000000000241 0x0000000000000001 0x000000000041083A 0x0000000000000001 0x0000000000000001 0x000000000041083A 0x0000000000000000 0x00000000002354F9 0x0000000000000002 ksqgtl: acquire TX-00070018-000001fe mode=X flags=GLOBAL|LONG why="row lock contention" C4048EBD:007F52B6    24   140 10005   2 KSL WAIT END [enq: TX - row lock contention] 1415053318/0x54580006 458776/0x70018 510/0x1fe time=2929879 C4048ED4:007F52B7    24   140 10005   1 KSL WAIT BEG [enq: TX - row lock contention] 1415053318/0x54580006 458776/0x70018 510/0x1fe C43146CA:007F535E    24   140 10005   2 KSL WAIT END [enq: TX - row lock contention] 1415053318/0x54580006 458776/0x70018 510/0x1fe time=2930676 ????????? ,PID=24 ??????ksqcmi???????? deadlock C43146D9:007F535F    24   140 10704 134 ksqcmi: performing local deadlock detection on TX-00070018-000001fe C43146F8:007F5360    24   140 10704 150 ksqcmi: deadlock not detected on TX-00070018-000001fe ?? ??? PID 17 ??ROLLBACK ???? ,????????: PID 17 ROLLBACK; D7A495BB:007F9D3E    17   142 10005   4 KSL POST SENT postee=24 loc='ksqrcl' id1=0 id2=0 name=   type=0 D7A495D8:007F9D3F    17   142 10444  12 ABORT TRANSACTION - xid: 0x0007.018.000001fe ??  PID 17 ??? TX resource?Enqueue Waiter linked List ???PID 24???,????KSL POST SENT ?? PID 24, ???ksqrcl???ENQUEUE LOCK ?PID 24??????KSL POST (KSL POST RCVD poster=17), ?ksqgtl???? TX-00070018-000001fe ?? ksqrcl??, ??PID 24???????? TX lock?USN ,??????? USN 3 XID 3.11.582 ,???acquire TX-0003000b-00000246 D7A49616:007F9D41    24   140 10005   3 KSL POST RCVD poster=17 loc='ksqrcl' id1=0 id2=0 name=   type=0 fac#=0 facpost=1 D7A4961C:007F9D42    24   140 10704  19 ksqgtl: SUCCESS D7A4967D:007F9D43    24   140 10704 117 ksqrcl: release TX-00070018-000001fe mode=X D7A496A5:007F9D44    24   140 10813   1 ktubnd: Bind usn 3 nax 1 nbx 0 lng 0 par 0 D7A496C2:007F9D45    24   140 10813   2 ktubnd: Txn Bound xid: 3.11.582 D7A496C7:007F9D46    24   140 10704  83 ksqgtl: acquire TX-0003000b-00000246 mode=X flags=GLOBAL|XACT why="contention" D7A496E4:007F9D47    24   140 10704  19 ksqgtl: SUCCESS ROW LOCK?Release ??????TX?ENQUEUE LOCK,?????????Process J ????????????, Process K??????????? ,Process K?????????,???row piece?lb??0×0 ,?????ITL,Process Z???ITL???????Process J????XID,?????Process J?????TX lock,PROCESS K ???TX resource?Enqueue Waiter Linked List?????X mode(exclusive)?enqueue lock? ???Process J??TX lock?,Process J?????TX resource?Enqueue Waiter Linked List ???Process K??????,??POST?????Process K? TX lock??????,???????row lock???????,?????????

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• Bigger ProjectServer farm is performing worse

  - by MSPS DBA

  I am using Project Server 2007 sp3 with SharePoint 2007 sp3 and SQL Server 2008 r2. I have recently moved my farm from 2 servers (1 DB and 1 App/Web) to a very big farm having Many Servers, Clustered Database, Load Balancer, Powerful processors and Large RAM. This Farm has more than one Web Servers, Project App Servers, SharePoint App Servers and a separate Index Server. But the performance of Project Server in the new Farm has been downgraded. Views are taking even more time to load data and Project publishing time has also been increased. I am also facing deadlock problems which are causing the project server queue jobs to fail. Could anyone inform me that what would be the reason of this problem and what should be the starting point to look into the issue? Is it mainly because now the application server needs to communicate with other application servers which were not needed in the previous farm? Thanks!

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• SSH running slow on cygwin

  - by Robb

  I have a Windows XP box with Cygwin running and the SSH service. I'd like to use PuTTY to connect to it from other computers on the local network. PuTTY works fine and I actually get a relatively speedy login prompt. But anytime I do an 'ls' on the root directory ('/') it typically doesn't complete, like the command is hung. Other PuTTY sessions suffer as well, no matter what i'm doing (even just an 'ls' on my home directory might take awhile or not finish). It is like a deadlock occurred somewhere in the ssh/cygwin system. The root directory does contain the 'cygdrive' folder which is the contents of the host computer. Could this be causing the slowdown?

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• July, the 31 Days of SQL Server DMO’s – Day 2 (sys.dm_exec_sessions)

  - by Tamarick Hill

    This sys.dm_exec_sessions DMV is another Server-Scoped DMV which returns information for each authenticated session that is running on your SQL Server box. Lets take a look at some of the information that this DMV returns. SELECT * FROM sys.dm_exec_sessions This DMV is very similar to the DMV we reviewed yesterday, sys.dm_exec_requests, and returns some of the same information such as reads, writes, and status for a given session_id (SPID). But this DMV returns additional information such as the Host name of the machine that owns the SPID, the program that is being used to connect to SQL Server, and the Client interface name. In addition to this information, this DMV also provides useful information on session level settings that may be on or off such as quoted identifier, arithabort, ansi padding, ansi nulls, etc. This DMV will also provide information about what specific isolation level the session is executing under and if the default deadlock priority for your SPID has been changed from the default. Lastly, this DMV provides you with an Original Login Name, which comes in handy whenever you have some type of context switching taking place due to an ‘EXECUTE AS’ statement being used and you need to identify the original login that started a session. For more information on this DMV, please see the below Books Online link: http://msdn.microsoft.com/en-us/library/ms176013.aspx

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• Following the Thread in OSB

  - by Antony Reynolds

  Threading in OSB The Scenario I recently led an OSB POC where we needed to get high throughput from an OSB pipeline that had the following logic: 1. Receive Request 2. Send Request to External System 3. If Response has a particular value   3.1 Modify Request   3.2 Resend Request to External System 4. Send Response back to Requestor All looks very straightforward and no nasty wrinkles along the way.  The flow was implemented in OSB as follows (see diagram for more details): Proxy Service to Receive Request and Send Response Request Pipeline   Copies Original Request for use in step 3 Route Node   Sends Request to External System exposed as a Business Service Response Pipeline   Checks Response to Check If Request Needs to Be Resubmitted Modify Request Callout to External System (same Business Service as Route Node) The Proxy and the Business Service were each assigned their own Work Manager, effectively giving each of them their own thread pool. The Surprise Imagine our surprise when, on stressing the system we saw it lock up, with large numbers of blocked threads.  The reason for the lock up is due to some subtleties in the OSB thread model which is the topic of this post.   Basic Thread Model OSB goes to great lengths to avoid holding on to threads.  Lets start by looking at how how OSB deals with a simple request/response routing to a business service in a route node. Most Business Services are implemented by OSB in two parts.  The first part uses the request thread to send the request to the target.  In the diagram this is represented by the thread T1.  After sending the request to the target (the Business Service in our diagram) the request thread is released back to whatever pool it came from.  A multiplexor (muxer) is used to wait for the response.  When the response is received the muxer hands off the response to a new thread that is used to execute the response pipeline, this is represented in the diagram by T2. OSB allows you to assign different Work Managers and hence different thread pools to each Proxy Service and Business Service.  In out example we have the “Proxy Service Work Manager” assigned to the Proxy Service and the “Business Service Work Manager” assigned to the Business Service.  Note that the Business Service Work Manager is only used to assign the thread to process the response, it is never used to process the request. This architecture means that while waiting for a response from a business service there are no threads in use, which makes for better scalability in terms of thread usage. First Wrinkle Note that if the Proxy and the Business Service both use the same Work Manager then there is potential for starvation.  For example: Request Pipeline makes a blocking callout, say to perform a database read. Business Service response tries to allocate a thread from thread pool but all threads are blocked in the database read. New requests arrive and contend with responses arriving for the available threads. Similar problems can occur if the response pipeline blocks for some reason, maybe a database update for example. Solution The solution to this is to make sure that the Proxy and Business Service use different Work Managers so that they do not contend with each other for threads. Do Nothing Route Thread Model So what happens if there is no route node?  In this case OSB just echoes the Request message as a Response message, but what happens to the threads?  OSB still uses a separate thread for the response, but in this case the Work Manager used is the Default Work Manager. So this is really a special case of the Basic Thread Model discussed above, except that the response pipeline will always execute on the Default Work Manager.   Proxy Chaining Thread Model So what happens when the route node is actually calling a Proxy Service rather than a Business Service, does the second Proxy Service use its own Thread or does it re-use the thread of the original Request Pipeline? Well as you can see from the diagram when a route node calls another proxy service then the original Work Manager is used for both request pipelines.  Similarly the response pipeline uses the Work Manager associated with the ultimate Business Service invoked via a Route Node.  This actually fits in with the earlier description I gave about Business Services and by extension Route Nodes they “… uses the request thread to send the request to the target”. Call Out Threading Model So what happens when you make a Service Callout to a Business Service from within a pipeline.  The documentation says that “The pipeline processor will block the thread until the response arrives asynchronously” when using a Service Callout.  What this means is that the target Business Service is called using the pipeline thread but the response is also handled by the pipeline thread.  This implies that the pipeline thread blocks waiting for a response.  It is the handling of this response that behaves in an unexpected way. When a Business Service is called via a Service Callout, the calling thread is suspended after sending the request, but unlike the Route Node case the thread is not released, it waits for the response.  The muxer uses the Business Service Work Manager to allocate a thread to process the response, but in this case processing the response means getting the response and notifying the blocked pipeline thread that the response is available.  The original pipeline thread can then continue to process the response. Second Wrinkle This leads to an unfortunate wrinkle.  If the Business Service is using the same Work Manager as the Pipeline then it is possible for starvation or a deadlock to occur.  The scenario is as follows: Pipeline makes a Callout and the thread is suspended but still allocated Multiple Pipeline instances using the same Work Manager are in this state (common for a system under load) Response comes back but all Work Manager threads are allocated to blocked pipelines. Response cannot be processed and so pipeline threads never unblock – deadlock! Solution The solution to this is to make sure that any Business Services used by a Callout in a pipeline use a different Work Manager to the pipeline itself. The Solution to My Problem Looking back at my original workflow we see that the same Business Service is called twice, once in a Routing Node and once in a Response Pipeline Callout.  This was what was causing my problem because the response pipeline was using the Business Service Work Manager, but the Service Callout wanted to use the same Work Manager to handle the responses and so eventually my Response Pipeline hogged all the available threads so no responses could be processed. The solution was to create a second Business Service pointing to the same location as the original Business Service, the only difference was to assign a different Work Manager to this Business Service.  This ensured that when the Service Callout completed there were always threads available to process the response because the response processing from the Service Callout had its own dedicated Work Manager. Summary Request Pipeline Executes on Proxy Work Manager (WM) Thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. Route Node Request sent using Proxy WM Thread Proxy WM Thread is released before getting response Muxer is used to handle response Muxer hands off response to Business Service (BS) WM Response Pipeline Executes on Routed Business Service WM Thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. No Route Node (Echo functionality) Proxy WM thread released New thread from the default WM used for response pipeline Service Callout Request sent using proxy pipeline thread Proxy thread is suspended (not released) until the response comes back Notification of response handled by BS WM thread so limited by setting of that WM.  If no WM specified then uses WLS default WM. Note this is a very short lived use of the thread After notification by callout BS WM thread that thread is released and execution continues on the original pipeline thread. Route/Callout to Proxy Service Request Pipeline of callee executes on requestor thread Response Pipeline of caller executes on response thread of requested proxy Throttling Request message may be queued if limit reached. Requesting thread is released (route node) or suspended (callout) So what this means is that you may get deadlocks caused by thread starvation if you use the same thread pool for the business service in a route node and the business service in a callout from the response pipeline because the callout will need a notification thread from the same thread pool as the response pipeline.  This was the problem we were having. You get a similar problem if you use the same work manager for the proxy request pipeline and a business service callout from that request pipeline. It also means you may want to have different work managers for the proxy and business service in the route node. Basically you need to think carefully about how threading impacts your proxy services. References Thanks to Jay Kasi, Gerald Nunn and Deb Ayers for helping to explain this to me.  Any errors are my own and not theirs.  Also thanks to my colleagues Milind Pandit and Prasad Bopardikar who travelled this road with me. OSB Thread Model Great Blog Post on Thread Usage in OSB

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• Runaway version store in tempdb

  - by DavidWimbush

  Today was really a new one. I got back from a week off and found our main production server's tempdb had gone from its usual 200MB to 36GB. Ironically I spent Friday at the most excellent SQLBits VI and one of the sessions I attended was Christian Bolton talking about tempdb issues - including runaway tempdb databases. How just-in-time was that?! I looked into the file growth history and it looks like the problem started when my index maintenance job was chosen as the deadlock victim. (Funny how they almost make it sound like you've won something.) That left tempdb pretty big but for some reason it grew several more times. And since I'd left the file growth at the default 10% (aaargh!) the worse it got the worse it got. The last regrowth event was 2.6GB. Good job I've got Instant Initialization on. Since the Disk Usage report showed it was 99% unallocated I went into the Shrink Files dialogue which helpfully informed me the data file was 250MB.  I'm afraid I've got a life (allegedly) so I restarted the SQL Server service and then immediately ran a script to make the initial size bigger and change the file growth to a number of MB. The script complained that the size was smaller than the current size. Within seconds! WTF? Now I had to find out what was using so much of it. By using the DMV sys.dm_db_file_space_usage I found the problem was in the version store, and using the DMV sys.dm_db_task_space_usage and the Top Transactions by Age report I found that the culprit was a 3rd party database where I had turned on read_committed_snapshot and then not bothered to monitor things properly. Just because something has always worked before doesn't mean it will work in every future case. This application had an implicit transaction that had been running for over 2 hours.

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• Dell XPS 15 L502x and Ubuntu 11.04 - HDMI output

  - by Jones

  Recently I've bought my dream's notebook, a Dell XPS 15 but since then this dream became a kind of endless nightmare. I'm almost getting crazy to make my graphic card driver work properly, but it seems to be just impossible. Yes, I have a 2GB NVIDIA GeForce GT 540m (Optimus) in it! It simply doesn't work. Every time I generate the xorg.conf Ubuntu hangs on while starting up, which forces me to remove this file to be able to start the notebook with the standard graphic settings. Another problem is that the Dell XPS 15 does NOT have a VGA output, but a HDMI. So, to be able to use a second monitor I have to configure it by the NVIDIA X Server Settings, which just works if the driver is properly initialized with the xorg.conf. I've also tried to make it work with the Bumblebee, but unfortunately it didn't help me much with the HDMI output. Do you guys have any idea to solve this deadlock? Is there any way for me to use my second monitor?

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• Java Desktop Application For Network users

  - by Motasem Abu Aker

  I'm developing a desktop application using Java. My application will run in a network environment where multiple users will access the same database through the application. There will be basic CRUD opreations (Insert, Update, Delete, & select), which means there will be chances of deadlock, or two users trying to update the same record at same time. I'm using the following Java Swing for Clients (MVC). MySQL Server for database (InnODB). Java Web start. Now, MySQL is centralized on the network, and all of the clients connect to it. The Application for ERP Purpose. I searched the internet to find a very good solution to ensure data integrity & to make sure that when updating one record from one client, other clients are aware of it. I read about Socket-server-client & RESTful web services. I don't want to go web application & don't want to use any extra libraries. So how can I handle this scenario: If User A updates a record: Is there a way to update User B's screen with the new value? If user A starts updating a record, how can I prevent other users from attempting to update the same record?

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• Set up Work Manager Shutdown Trigger in WebLogic Server 10.3.4 Using WLST

  - by adejuanc

  WebLogic Server's Work Managers provide a way to control work and allocated threads. You can set different scheduling guidelines for different applications, depending on your requirements. There is a default self-tuning Work Manager, but you might want to set up a custom work manager in some circumstances: for example, when you want the server to prioritize one application over another when a response time goal is required, or when a minimum thread constraint is needed to avoid deadlock. The Work Manager Shutdown Trigger is a tool to help with stuck threads in which will do the following: Shut down the Work Manager. Move the application to Admin State (not active). Change the Server instance health state to failed. Example of a Shutdown Trigger set on the config.xml for your domain: <work-manager>   <name>stuckthread_workmanager</name>   <work-manager-shutdown-trigger>     <max-stuck-thread-time>30</max-stuck-thread-time>     <stuck-thread-count>2</stuck-thread-count>   </work-manager-shutdown-trigger> </work-manager> Understand that any misconfiguration on the Work Manager can lead to poor performance on the server. Any changes must be done and tested before going to production. How can one create a WorkManagerShutdownTrigger for WLS 10.3.4 using WLST? You should be able to create a WorkManagerShutdownTrigger using WLST by following these steps: edit() startEdit() cd('/SelfTuning/mydomain/WorkManagers') create('myWM','WorkManager') cd('myWM/WorkManagerShutdownTrigger') create('myWMst','WorkManagerShutdownTrigger') cd('myWMst') ls()

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• How exactly to implement multiple threads in a game

  - by xerwin

  So I recently started learning Java, and having a interest in playing games as well as developing them, naturally I want to create game in Java. I have experience with games in C# and C++ but all of them were single-threaded simple games. But now, I learned how easy it is to make threads in Java, I want to take things to the next level. I started thinking about how would I actually implement threading in a game. I read couple of articles that say the same thing "Usually you have thread for rendering, for updating game logic, for AI, ..." but I haven't (or didn't look hard enough) found example of implementation. My idea how to make implementation is something like this (example for AI) public class AIThread implements Runnable{ private List<AI> ai; private Player player; /*...*/ public void run() { for (int i = 0; i < ai.size(); i++){ ai.get(i).update(player); } Thread.sleep(/* sleep until the next game "tick" */); } } I think this could work. If I also had a rendering and updating thread list of AI in both those threads, since I need to draw the AI and I need to calculate the logic between player and AI(But that could be moved to AIThread, but as an example) . Coming from C++ I'm used to do thing elegantly and efficiently, and this seems like neither of those. So what would be the correct way to handle this? Should I just keep multiple copies of resources in each thread or should I have the resources on one spot, declared with synchronized keyword? I'm afraid that could cause deadlocks, but I'm not yet qualified enough to know when a code will produce deadlock.

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