Informix halts for no obvious reason ?!

Hi, folks. This is the umpteenth time this happens, so I wonder if anyone can help. Even a few hints will be more than welcome. When the system is busy enough ( 20-30 users of Informix ) and people start issuing "heavy" queries, Informix falls into a strange deadlock. It looks like one process is in a critical section, and won't leave it. Informix waits for this process to get out of its critical section, so that it can complete the pending checkpoint. In the end, all users end up waiting for this checkpoint, which never occurs. It happens to random users, using random programs, i.e. there is no any consistency about this behaviour. Here is some information about our version of Informix, etc. ====================================================== Database: Informix OnLine 5.0.2.UC6 OS : SCO OpenServer Enterprise System Release 3.0 E-mail : dbadmin@svilosa.bis.bg ====================================================== The following is a listing of a file containing a snapshot of the system at the time of the failure: RSAM Version 5.01.UD2 -- On-Line (CKPT REQ) -- Up 01:14:09 -- 20288 Kbytes Message Log File: /usr/runtime/online.log ted 08:10:22 Checkpoint Completed 08:10:27 Checkpoint Completed 08:14:11 Checkpoint Completed 08:14:13 Checkpoint Completed 08:14:16 Checkpoint Completed 08:14:22 Checkpoint Completed 08:14:26 Checkpoint Completed 08:14:30 Checkpoint Completed 08:14:34 Checkpoint Completed 08:15:43 Checkpoint Completed 08:17:30 Checkpoint Completed 08:18:18 Checkpoint Completed 08:18:35 Checkpoint Completed 08:19:53 Checkpoint Completed 08:25:04 Checkpoint Completed 08:28:10 Checkpoint Completed Configuration File: /usr/runtime/etc/tbconfig #************************************************************************** # # INFORMIX SOFTWARE, INC. # # Title: tbconfig.std # Sccsid: @(#)tbconfig.std 9.1.1.1 1/11/92 19:15:16 # Description: INFORMIX-OnLine Configuration Parameters # #************************************************************************** # Root Dbspace Configuration ROOTNAME rootdbs # Root dbspace nameROOTPATH /usr/runtime/chunks/Chunk1 # Path for device containing root dbspace ROOTOFFSET 50 # Offset of root dbspace into device (Kbytes) ROOTSIZE 683000 # Size of root dbspace (Kbytes) # Disk Mirroring Configuration MIRROR 0 # Mirroring flag (Yes = 1, No = 0) MIRRORPATH # Path for device containing root dbspace mirror MIRROROFFSET 0 # Offset into mirror device (Kbytes) # Physical Log Configuration PHYSDBS rootdbs # Name of dbspace that contains physical log PHYSFILE 1000 # Physical log file size (Kbytes) # Logical Log Configuration LOGFILES 50 # Number of logical log files LOGSIZE 1000 # Size of each logical log file (Kbytes) # Message Files MSGPATH /usr/runtime/online.log # OnLine message log pathname CONSOLE /dev/console # System console message pathname # Archive Tape Device TAPEDEV /dev/urStp1 # Archive tape device pathname TAPEBLK 16 # Archive tape block size (Kbytes) TAPESIZE 2000000 # Max amount of data to put on tape (Kbytes) # Logical Log Backup Tape Device LTAPEDEV /dev/rStp1 # Logical log tape device pathname LTAPEBLK 16 # Logical log tape block size (Kbytes) LTAPESIZE 2000000 # Max amount of data to put on log tape (Kbytes) # Identification Parameters SERVERNUM 1 # Unique id associated with this OnLine instance DBSERVERNAME runtime # Unique name of this OnLine instance # Shared Memory Parameters RESIDENT 1 # Forced residency flag (Yes = 1, No = 0)USERS 40 # Maximum number of concurrent user processes TRANSACTIONS 150 # Maximum number of concurrent transactions LOCKS 50000 # Maximum number of locks BUFFERS 8000 # Maximum number of shared memory buffersTBLSPACES 400 # Maximum number of active tblspaces CHUNKS 8 # Maximum number of chunks DBSPACES 8 # Maximum number of dbspaces and blobspaces PHYSBUFF 32 # Size of physical log buffers (Kbytes) LOGBUFF 32 # Size of logical log buffers (Kbytes)LOGSMAX 50 # Maximum number of logical log files CLEANERS 1 # Number of page-cleaner processes SHMBASE 0x0 # Shared memory base address CKPTINTVL 300 # Checkpoint interval (in seconds) LRUS 8 # Number of LRU queues LRU_MAX_DIRTY 60 # LRU modified begin-cleaning limit (percent) LRU_MIN_DIRTY 50 # LRU modified end-cleaning limit (percent) LTXHWM 65 # Long TX high-water mark (percent) LTXEHWM 75 # Long TX exclusive high-water mark (percent) # Machine- and Product-Specific Parameters DYNSHMSZ 0 # Dynamic shared memory size (Kbytes) GTRID_CMP_SZ 32 # Number of bytes to use in GTRID comparision DEADLOCK_TIMEOUT 60 # Max time to wait for lock in distributed env. TXTIMEOUT 300 # Transaction timeout for I-STAR (in seconds)SPINCNT 0 # No. of times process tries for latch STAGEBLOB # Reserved for INFORMIX-OnLine/Optical # System Page Size BUFFSIZE 2048 # Page size (do not change!) Users address flags pid user tty wait tout locks nreads nwrites 804019f0 C-----D 385 root console 0 0 0 364 22 80401a60 ------D 0 root console 0 0 0 0 0 80401ad0 ------F 389 root 0 0 0 0 0 80401b40 S------ 725 bos ttyp1 8040154c 0 0 172 1 80401bb0 --A---M 730 informix tty05 0 0 0 0 0 80401c20 S------ 1439 nadja ttyp0 8040154c 0 2 64 5 80401c90 S------ 1350 skt ttya13 8040154c 0 12 97 0 80401d00 S------ 938 eti ttyp3 8040154c 0 8 337 81 80401d70 S------ 1470 nadja ttyp0 8040154c 0 0 0 0 80401de0 S------ 1467 magda ttya18 8040154c 0 3 0 0 80401e50 S------ 1233 ceca ttyp5 8040154c 0 3 16699 209 80401ec0 S------ 1472 bos ttyp2 8040154c 0 3 2 0 80401f30 S------ 1466 rum ttya16 8040154c 0 2 9 0 80401fa0 S------ 1306 informix ttyp6 8040154c 0 2 4 0 80402010 C-B---- 1391 trufi ttya07 0 0 15 163 8 80402080 ------- 1419 marica ttya03 0 0 3 400 30 804020f0 B-B-X-- 1415 petkova ttya01 80644010 0 3 3395 26 80402160 S------ 152