2536969 - 'ev_iqmpxstatus' worked very slow and resulted in Coordinator's unresponsive status -- SAP IQ

System event "ev_iqmpxstatus" looked to work very slow for a long time and never finished. It seemed Coordinator server goes to hang up status, even though it was working when saw stack flow. From the output of sp_iqtransaction (running it at '2017-09-12 15:07'), the status of "ev_iqmpxstatus" was "ACTIVE". Because of the event problem, number of other versions were growing larger and all servers in the multiplex became slower.

•   iqmsg
    
      I. 09/12 00:32:53. 0001326136 ev_iqmpxstatus started ...
      I. 09/12 00:34:00. 0001326168 ev_iqmpxstatus started ...
      I. 09/12 00:35:00. 0001326203 ev_iqmpxstatus started ...
      I. 09/12 00:36:00. 0001326237 ev_iqmpxstatus started     <== last ev_iqmpxstatus execution and not finished
      ...
      ...
      I. 09/12 11:24:39. 0001332338 Cancellation request received:  SA connHandle: 1001089805  SA connID: 72  IQ connID: 0001326237  User: dbo
      ...
•   Stack 

   When tracing 139673742931712 (IQ connID: 0001326237) -- last ev_iqmpxstatus session,
   this thread showed mostly same doing 'hos_pi_pwrite'.
   But sometimes the thread worked shortly other operation 'GetSaintForbidLatch()'.
   It seems the thread was working slowly, rather than hang-up.
   
    == Thread Number  139673742931712  (IQ connID: 0001326237) ====
    
    * stktrc-20170912-130542 =>
    
      .. hos_pi_pwrite(hos_fd, void const*, ..
      .. hos_svbio::Write(unsigned long long, ..
      .. hos_mvbio::Write(unsigned long long, ..
      .. s_buf::WriteBufToDisk
   
    * stktrc-20170912-151240 =>
   
      .. hos_condvar::Wait()+0x2f
      .. st_database::GetSaintForbidLatch()+0x5d
      .. st_connection::GetForbid()+0x1a
      .. st_connection::GetIQForbid(int)+0x51

    * stktrc-20170912-161644 =>
   
      .. hos_pi_pwrite(hos_fd, void const*, ..
      .. hos_svbio::Write(unsigned long long, ..
      .. hos_mvbio::Write(unsigned long long, ..
      .. s_buf::WriteBufToDisk

• SAP IQ16.0 SP08.x
• SAP IQ16.0 SP11.x

"hos_pi_pwrite" , "GetSaintForbidLatch", CR814594, CR#814594, 814594,  ev_iqmpxstatus, iqmpxstatus , 810859 , 757402 , KBA , BC-SYB-IQ , Sybase IQ , Bug Filed