long checkpoints

hello all, we have recently experienced checkpoints that are lasting 20-30 seconds that were previously 5-8 seconds. I am looking at the CONFIG file to see if something could be improved. We are on HP-UNIX box (11.00)(2 proc box) with Informix 9.21 HC-5. BUFFERS 250000 # Maximum number of shared buffers NUMAIOVPS 2 # Number of IO vps PHYSBUFF 32 # Physical log buffer size (Kbytes) LOGBUFF 32 # Logical log buffer size (Kbytes)LOGSMAX 40 # Maximum number of logical log files CLEANERS 50 # Number of buffer cleaner processes LRUS 50 # Number of LRU queues LRU_MAX_DIRTY 30 # LRU percent dirty begin cleaninglimit LRU_MIN_DIRTY 25 # LRU percent dirty end cleaning limit CKPTINTVL 300 # Check point interval (in sec) MULTIPROCESSOR 1 # 0 for single-processor, 1 formulti-processor NUMCPUVPS 2 # Number of user (cpu) vps SINGLE_CPU_VP 0 # If non-zero, limit number of cpu vpsto one LTXHWM 50 # Long transaction high water markpercentage LTXEHWM 60 # Long transaction high water mark (exclusive) KAIO is enabled. thanks for any help......