From the config info you supplied: Sparc 20, Solaris 2.5, 64MB RAM
Informix 7.x?
Hardware: More RAM, 64MB more, and allocate more RAM to informix.
The config info is too little to give detailed solutions. Need the
Informix config file, what disk, scsi, how many users, some onstat stuff,
locations of large heavy use tables.
Try running 'update statistics' on dynamic tables, maybe in crontab at
a low activity time once a day. Read the manual on performance tips.