Disabling clustering for session attributes presumes the presence of a sticky load balancer (as the non-clustered attributes will be visible only to requests executing locally within that JVM).
Implement the interface HttpSessionCollection.SessionDistributionController (in package com.tangosol.coherence.servlet, in the coherence-web.jar found in webInstaller.jar). The specific method of interest is isSessionAttributeDistributed().
After the "inspect" phase of the Coherence*Web installation process, edit the coherence-web.xml that is generated. Specify the distribution controller: