Informix Tuning Problem

My server run very slow for this few weeks.. I've checked the %cache go 99%.. Hardware : IBM - H80 , 4 CPU , 2G Ram , HD x 2 dskreads pagreads bufreads %cached dskwrits pagwrits bufwrits %cached 25899 119543 30538756 99.92 97670 146260 2077545 95.30 ONCONFIG : - MULTIPROCESSOR 1 # 0 for single-processor, 1 for multi-processor NUMCPUVPS 4 # Number of user (cpu) vps SINGLE_CPU_VP 0 # If non-zero, limit number of cpu vps to one LOCKS 150000 # Maximum number of locks BUFFERS 80000 # Maximum number of shared buffers NUMAIOVPS 2 # Number of IO vps PHYSBUFF 1024 # Physical log buffer size (Kbytes) LOGBUFF 500 # Logical log buffer size (Kbytes)LOGSMAX 25000 # Maximum number of logical log files CLEANERS 8 # Number of buffer cleaner processes SHMBASE 0x30000000 # Shared memory base address SHMVIRTSIZE 98304 # initial virtual shared memory segment size SHMADD 32768 # Size of new shared memory segments (Kbytes) SHMTOTAL 524288 # Total shared memory (Kbytes). 0=>unlimited CKPTINTVL 120 # Check point interval (in sec) LRUS 8 # 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) Any idea ?