IT33322: CDE QUERY SEEMS HANGING, IT DOESN'T COMPLETE IN HOURS WHEN IT NORMALLY COMPLETES IN MINUTES THE CAUSE IS CDE PARADISE SORT HANGS

APAR status

• Closed as program error.

Error description

• The issue is a race condition caused by a lack of memory
  barriers when barrierWaitInterruptible() is used.  The unused
  function barrierWait() may also have a similar issue, and that
  will be fixed as well.
  
  The hang includes the following stacks:
  
  ================================================================
  ================
  === 35184.248967.014.stack.txt:                          248967
  - db2agntcol (BLUDB) 14 [-]
  0x000010001664FF80 ossWasteTime + 0x0050
  0x0000100009A12B68
  ibm_cde::query::NativeSortCB::paradisSort(ibm_cde::query::NSJob*
  , unsigned long) + 0x0f38
  0x0000100009A1135C ibm_cde::query::NativeSortCB::sort(unsigned
  int) + 0x0d0c
  0x000010000996479C
  ibm_cde::query::SortEvaluator::sortPartition(ibm_cde::query::Sor
  tPartition*) + 0x014c
  0x00001000099628B0
  ibm_cde::query::SortEvaluator::processInputsSynchronously() +
  0x0590
  0x0000100006CA685C ibm_cde::query::Evaluator::evaluate(bool,
  bool, ibm_cde::query::Evaluator::EvaluatorRestartState&,
  ibm_cde::query::OptPredicateTracker*) + 0x088c
  0x0000100006BA279C
  ibm_cde::query::EvaluationRoutine::evaluate(unsigned int,
  sql_static_data*) + 0x03ac
  0x0000100007AC3E88
  ibm_cde::query::Scheduler::evaluateChain(ibm_cde::query::Evaluat
  ionRoutine*, unsigned long&, unsigned int) + 0x0418
  0x0000100007AC0F18
  ibm_cde::query::Scheduler::runWorkerThread(void*, int*) + 0x03b8
  0x0000100007AC8CDC ibm_cde::query::cdeEntryPointImpl(sqeAgent*,
  void*, void*) + 0x00bc
  0x0000100008CFBFDC cdeInterface::startCdeSubagent(sqeAgent*) +
  0x00ec
  0x000010000F214384 sqlriInvokeCde(sqlrr_cb*) + 0x0064
  0x000010000F0487F0 sqlriSectInvoke(sqlrr_cb*, sqlri_opparm*) +
  0x0410
  
  
  ================================================================
  ================
  === 35184.226015.014.stack.txt:                          226015
  - db2agntcol (BLUDB) 14 [-]
  === 35184.226037.014.stack.txt:                          226037
  - db2agntcol (BLUDB) 14 [-]
  === 35184.248731.014.stack.txt:                          248731
  - db2agntcol (BLUDB) 14 [-]
  === 35184.249369.014.stack.txt:                          249369
  - db2agntcol (BLUDB) 14 [-]
  0x00001000000942B8 __nanosleep + 0x0088
  0x0000100009A107EC ibm_cde::query::NativeSortCB::sort(unsigned
  int) + 0x019c
  0x000010000996479C
  ibm_cde::query::SortEvaluator::sortPartition(ibm_cde::query::Sor
  tPartition*) + 0x014c
  0x00001000099628B0
  ibm_cde::query::SortEvaluator::processInputsSynchronously() +
  0x0590
  0x0000100006CA685C ibm_cde::query::Evaluator::evaluate(bool,
  bool, ibm_cde::query::Evaluator::EvaluatorRestartState&,
  ibm_cde::query::OptPredicateTracker*) + 0x088c
  0x0000100006BA279C
  ibm_cde::query::EvaluationRoutine::evaluate(unsigned int,
  sql_static_data*) + 0x03ac
  0x0000100007AC3E88
  ibm_cde::query::Scheduler::evaluateChain(ibm_cde::query::Evaluat
  ionRoutine*, unsigned long&, unsigned int) + 0x0418
  0x0000100007AC0F18
  ibm_cde::query::Scheduler::runWorkerThread(void*, int*) + 0x03b8
  0x0000100007AC8CDC ibm_cde::query::cdeEntryPointImpl(sqeAgent*,
  void*, void*) + 0x00bc
  0x0000100008CFBFDC cdeInterface::startCdeSubagent(sqeAgent*) +
  0x00ec
  0x000010000F214384 sqlriInvokeCde(sqlrr_cb*) + 0x0064
  0x000010000F0487F0 sqlriSectInvoke(sqlrr_cb*, sqlri_opparm*) +
  0x0410
  
  This is on power pc which is heavily inlined.
  There may be some barrier related functions on the stack between
  paradisSort and ossWasteTime on other platforms.
  

Local fix

• There are 2 possible workarounds:
  
  1)Re-submitting the query, with a different system workload may
  works.
  
  2)The using of the following Registry setting :
  
  db2set DB2_REDUCED_OPTIMIZATION=COL_NO_OLAP
  
  or passing it to the query in  embedded guidelines :
  
  /* <OPTGUIDELINES>
  <REGISTRY>
  <OPTION NAME='DB2_REDUCED_OPTIMIZATION' VALUE='COL_NO_OLAP'/>
  </REGISTRY>
  </OPTGUIDELINES>*/
  

Problem summary

• ****************************************************************
  * USERS AFFECTED:                                              *
  * All                                                          *
  ****************************************************************
  * PROBLEM DESCRIPTION:                                         *
  * See Error Description                                        *
  ****************************************************************
  * RECOMMENDATION:                                              *
  * None                                                         *
  ****************************************************************
  

Problem conclusion

• The fix will be included into DB2 11.1 Fix Pack m4fp6
  

Temporary fix

Comments

APAR Information

• APAR is sysrouted FROM one or more of the following:

• APAR is sysrouted TO one or more of the following:

Fix information

• Fixed component name

  DB2 FOR LUW

• Fixed component ID

  DB2FORLUW

Applicable component levels