If BO servers and Tomcat are not clustered, then you will face this problem. But still you can improve your server performance like increasing the APS heap memory to 4g(-Xmx 4g).
please find the basic first steps for tuning your environment.
1694041 - BI 4.0 Consulting:- How to size the Adaptive Processing Server
1640036 Added memory usage when splitting Adaptive Processing Server (APS) services
1580280 Adaptive Processing Server and Adaptive Job Server in SAP BI 4.0 are using high amounts of memory and are hard to manage and troubleshoot
please check the below note as well..
1570271 - How to find Sizing information for SAP Business Objects Products