Domino on RedHAt Linux +Memory usage issue

Hi All, We are using Domino 6.5.3 on RedHat Linux Enterprise Edtion 3 (update5) .Server RAM is 2 GB .The Domino server is in cluster with another Domino server with same configuration .Lately we have been observing that the RAM usage is very high in both server and the server tasks is showing the Database server(using sh task command in Domino console ) using multiple instances even when the server .This is using up the server memory resources and the RAm usage is 1.8 GB

Kindly advise us how to free the server memory .FYi the number of users is 2-3 when this is happening as this is a new setup.

Regards,

TS