Our Sun E450 system seems slow, especially when 20 users log in together to our Baan ERP system. The physical RAM is 640MB and the disk space has about 57 percent capacity left. Why is the system slow, and what should I do the make it better?
There's not anywhere near enough info here to make any recommendations, but I can give you some places to start.
First of all, have your sys admin check the kernel parameters and compare them with those listed in $INFORMIXDIR/release. Have him or her also use some UNIX performance monitoring tools such as sar or top to see if you are exhausting any of your resources or hitting any kernel limits when you have 20 users on the system. Watch especially for any signs of swapping. If you're swapping when you get many users on the system, increase your kernel parameters.
If logins and initial connections are the slow parts, you may want to consider monitoring your network and using the onstat -g ntt options to see what's happening at the network level.
Once you have these issues handled, then start looking at actual database performance. As I said, there's not anywhere enough info here to make any assessments. Read the sections of the performance tuning manual and see if anything fits your symptoms.