bad performance on delete

On Informix 7.23, when deleting records on large tables it goes very slow. What should we change to get better performance? $ onstat -p INFORMIX-OnLine Version 7.22.UC2 -- On-Line -- Up 01:06:01 -- 130680 Kbytes Profile dskreads pagreads bufreads %cached dskwrits pagwrits bufwrits %cached 44588 44727 15176613 99.71 3330 5595 10658 68.76 isamtot open start read write rewrite delete commit rollbk 284423 731 4473 258214 753 2 2705 1295 0 ovlock ovuserthread ovbuff usercpu syscpu numckpts flushes 0 0 0 726.41 2.63 4 12 bufwaits lokwaits lockreqs deadlks dltouts ckpwaits compress seqscans 1526 0 56023660 0 0 0 1 618 ixda-RA idx-RA da-RA RA-pgsused lchwaits 1424 9116 32210 42706 30 $ onstat -g glo INFORMIX-OnLine Version 7.22.UC2 -- On-Line -- Up 01:06:26 -- 130680 Kbytes MT global info: sessions threads vps lngspins 1 18 11 3 sched calls thread switches yield 0 yield n yield forever total:7645421 47167 7600110 10098 12035 per sec:10 6 4 3 0 Virtual processor summary: class vps usercpu syscpu total cpu 2 747.94 1.90 749.84 aio 4 2.02 0.65 2.67 tli 1 0.00 0.00 0.00 lio 1 0.00 0.10 0.10 pio 1 0.80 0.01 0.81 adm 1 0.00 0.00 0.00 msc 1 0.15 0.00 0.15 total 11 750.91 2.66 753.57 Individual virtual processors: vp pid class usercpu syscpu total 1 7183 cpu 12.12 1.49 13.61 2 7184 adm 0.00 0.00 0.00 3 7185 cpu 735.82 0.41 736.23 4 7186 lio 0.00 0.10 0.10 5 7187 pio 0.80 0.01 0.81 6 7188 aio 0.65 0.25 0.90 7 7189 msc 0.15 0.00 0.15 8 7190 aio 0.06 0.16 0.22 9 7191 aio 0.64 0.16 0.80 10 7192 aio 0.67 0.08 0.75 11 7193 tli 0.00 0.00 0.00 tot 750.91 2.66 753.57 $ onstat -g sch INFORMIX-OnLine Version 7.22.UC2 -- On-Line -- Up 01:06:59 -- 130680 Kbytes VP Scheduler Statistics: vp pid class semops busy waits spins/wait 1 7183 cpu 1 26 3946 2 7184 adm 0 0 0 3 7185 cpu 7941 8391 9854 4 7186 lio 1401 0 0 5 7187 pio 128 0 0 6 7188 aio 2225 0 0 7 7189 msc 17 0 0 8 7190 aio 1457 0 0 9 7191 aio 1049 0 0 10 7192 aio 825 0 0 11 7193 tli 2 2 1000 $ sar 1 5 UnixWare customs01 5 7.1.0 i386 03/28/05 12:44:46 %usr %sys %wio %idle %intr 12:44:47 50 0 0 50 0 12:44:48 50 0 0 50 0 12:44:49 50 0 0 50 0 12:44:50 50 0 0 50 0 12:44:51 46 0 12 42 0 Average 49 0 2 48 0 It's on dual processor Porliant ML350 with 512 MB memory ONCONFIG: # Physical Log Configuration PHYSDBS rootdbs # Location (dbspace) of physical log PHYSFILE 100000 # Physical log file size (Kbytes) # Logical Log Configuration LOGFILES 9 # Number of logical log files LOGSIZE 50000 # Logical log size (Kbytes) # System Configuration SERVERNUM 0 # Unique id corresponding to a OnLine instance DBSERVERNAME customs01 # Name of default database server DBSERVERALIASES customs # List of alternate dbservernames NETTYPE ipcshm,1,350,CPU # Configure poll thread(s) for nettype DEADLOCK_TIMEOUT 60 # Max time to wait of lock in distributed env. RESIDENT 1 # Forced residency flag (Yes = 1, No = 0) MULTIPROCESSOR 1 # 0 for single-processor, 1 for multi-processor NUMCPUVPS 2 # Number of user (cpu) vps SINGLE_CPU_VP 0 # If non-zero, limit number of cpu vps to one NOAGE 0 # Process aging AFF_SPROC 0 # Affinity start processor AFF_NPROCS 0 # Affinity number of processors # Shared Memory Parameters LOCKS 200000 # Maximum number of locks BUFFERS 50000 # Maximum number of shared buffers NUMAIOVPS 4 # Number of IO vps PHYSBUFF 32 # Physical log buffer size (Kbytes) LOGBUFF 32 # Logical log buffer size (Kbytes)LOGSMAX 10 # Maximum number of logical log files CLEANERS 2 # Number of buffer cleaner processes SHMBASE 0xa000000 # Shared memory base address SHMVIRTSIZE 8000 # initial virtual shared memory segment size SHMADD 8192 # Size of new shared memory segments (Kbytes) SHMTOTAL 0 # Total shared memory (Kbytes). 0=>unlimited CKPTINTVL 900 # Check point interval (in sec) LRUS 32 # Number of LRU queues LRU_MAX_DIRTY 60 # LRU percent dirty begin cleaning limit LRU_MIN_DIRTY 50 # LRU percent dirty end cleaning limit LTXHWM 50 # Long transaction high water mark percentage LTXEHWM 60 # Long transaction high water mark(exclusive) TXTIMEOUT 0x12c # Transaction timeout (in sec) STACKSIZE 32 # Stack size (Kbytes) # Read Ahead Variables RA_PAGES 32 # Number of pages to attempt to read ahead RA_THRESHOLD 16 # Number of pages left before next group FILLFACTOR 90 # Fill factor for building indexes # Parallel Database Queries (pdq) MAX_PDQPRIORITY 10 # Maximum allowed pdqpriority DS_MAX_QUERIES 500 # Maximum number of decision supportqueries DS_TOTAL_MEMORY 65536 # Decision support memory (Kbytes) DS_MAX_SCANS 1048576 # Maximum number of decision supportscans DATASKIP off # List of dbspaces to skip OPTCOMPIND 0 # To hint the optimizer ONDBSPACEDOWN 2 # Dbspace down option: 0 = CONTINUE, 1 = ABORT, 2 = WAITLBU_PRESERVE 0