For a cluster of servers that span multiple systems in a sysplex, and that will have stateful session beans with an activation policy of Transaction deployed in them, the passivation directory should reside on an HFS (hierarchical file system) that is shared across the multiple systems in the sysplex on which the clustered servers will be running.
If you answered yes to all the questions above, then you should define a shared HFS (hierarchical file system) to be used as the passivation directory for the stateful session beans.
/WebSphere/V6R0M0/AppServer/passivation/cluster1
For optimal performance, you should create a passivation directory for each cluster. Also, the default passivation directory should not be used for clusters; it should be used for non-clustered servers and servers that do not have stateful session beans with an activation policy of Transaction.
For information about defining a shared HFS, see z/OS® UNIX System Services Planning.
Read the topic on EJB container settings for information on specifying the passivation directory with the administrative console.