INFORMIX SERVER / 5725A3900 / C10 - IDS 12.10

Running Update Statistics Low with USTLOW_SAMPLE enabled will
crash the engine when exiting with "Thread exited with # buffers
held", if on a big index data skew is found.

You'll get a warning in the online.log about the inaccurate
index statistics.

13:30:51  Warning: update statistics low using sampling may
generate inaccurate index statistics for index informix.xxxxxx
due to data skew

14:54:40
14:54:40  IBM Informix Dynamic Server Version 12.10.FC6X5WE
Software Serial Number AAA#B000000

14:54:40  Assert Failed: Thread exited with 2 buffers held.

14:54:40   Who: Session(193, informix@xxxxxxx, 19844,
0x4db7a550)
		Thread(227, sqlexec, 4db3dde8, 1)
		File: rsshmem.c Line: 2083
14:54:40   Results: Dynamic Server must abort
14:54:40  SHM Globals and Master Pool/Master Block Adresses:

14:54:40  shmcb =           0x000000004419dc28
14:54:40  rhead =           0x000000004420a800
14:54:40  pool list =       0x000000004419dd00
14:54:40  block pool list = 0x0000000044204908
14:54:40  TRANSP =          0x000000004db7a550
14:54:40  PARTP =           0x0000000000000000
14:54:40  PARTNP =          0x0000000000000000
14:54:40  OPENP =           0x000000004f1d9828
14:54:40  FILEP =           0x000000004f1dd4e0
14:54:40  Raw hex dump of stack located in
/opt/informix/tmp/af.4cbedff.rawstk
14:54:40  Stack for thread: 227 sqlexec

 base: 0x000000004f1f4000
  len:   69632
   pc: 0x00000000013f50e7
  tos: 0x000000004f202b50
state: running
   vp: 1

(/opt/informix/bin/oninit) afstack
(/opt/informix/bin/oninit) afhandler
(/opt/informix/bin/oninit) afcrash_interface
(/opt/informix/bin/oninit) rstcb_cleanup
(/opt/informix/bin/oninit) destroy_session
(/opt/informix/bin/oninit) sq_exit
(/opt/informix/bin/oninit) sqmain
(/opt/informix/bin/oninit) spawn_thread
(/opt/informix/bin/oninit) th_init_initgls
0x000000000144e858 (/opt/informix/bin/oninit) startup

Onstat -b shows:

===========------------- - - - - - -
/opt/informix/bin/onstat -b:

IBM Informix Dynamic Server Version 12.10.FC6X5WE -- On-Line --
Up 03:18:23 -- 3573872 Kbytes

Buffers
address           userthread        flgs pagenum
memaddr           nslots pgflgs xflgs owner             waitlist


Buffer pool page size: 2048
71a972d8         0                802  5:3432386        7e954000
0      2890   10    0                0
7ade6598         0                802  5:6639819        f46e3000
22     890    10    0                0
 45 modified, 1310720 total, 2097152 hash buckets, 2048 buffer
size

and those pagenum belongs to index(es) for table reported,
including the index reported on the warning.

not known / see Local fix

This APAR is a duplicate of IT13966

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

18.07.2016
09.12.2016
09.12.2016