2178702 - Multiplex writer node update causes hang - SAP IQ 15.2

• Update transaction running in a SAP IQ 15.2 MPX writer node is not responding or completing
• Subsequent transactions that need to update the same tables become stuck waiting on the initially hung transaction to complete 
• Monitoring output from stored procedure sp_iqtransaction, sp_iqcontext and sp_iqlocks shows a long running update transaction stuck with an OPENCURSOR in a PREPARED state that does not move.  It will also show subsequent transactions requiring locks on the same table resources becoming stuck waiting on the completion of the initial transaction.   
• Eventually all connections and context slots in the IQ server become full and no further connections are serviced giving the impression that the entire IQ server is now hung 
• Capturing pstacks of the IQ process show one or more threads stuck in a loop on a call to s_phash::ReHashInternal similar to the following

-----------------  lwp# 166 / thread# 166  --------------------
 fffffd7fe68b370a __1cHs_phashOReHashInternal6M_i_ () + 110a
 fffffd7fe68aa38d __1cHs_phashRInsertKeyIfUnique6MpkpknJhos_datum__i_ () + 2d
 fffffd7fe5d7ab52 __1cUdfe_ManyCachedValuesIEvaluate6M_v_ () + b2
 fffffd7fe5d9a455 __1cSdfe_CountAggregateJNextValue6M_v_ () + 65
 fffffd7fe5f10738 __1cSdfo_GroupByOrderedJFetchOpus6M_i_ () + 678
 fffffd7fe5e8b08e __1cPdfjo_HashParaT1JFetchOpus6M_i_ () + 6fe
 fffffd7fe5fa3aab __1cSdfo_cOrderByParaInIExecWork6MriI_i_ () + 51b
 fffffd7fe63af9e6 __1cNworkAllocatorGDoWork6MI_v_ () + 216
 ......
 fffffd7ffe8f55b5 ???????? ()
 fffffd7ffe10da9b _thr_setup () + 5b
 fffffd7ffe10dcd0 _lwp_start () 

• Eventually the server may become unresponsive and requires a kill and restart which clears the problem.

SAP IQ 15.2

KBA , BC-SYB-IQ , Sybase IQ , Problem