Solution : https://service.sap.com/sap/support/notes/905211 (SAP Service marketplace login required)
Key words : 
/saphelp_nw70/helpdata/en/2a/edece171d547449ab0e1d295f3b0bc/frameset, aggressive softreference garbage collection policy, aggressive softreference collection policy configuration, solution suboptimal cache efficiency caused, high weight recommended configuration settings, pcd cache optimizer configuration parameters, sap solution manager diagnostics -, background thread periodically traverses, ensure stable runtime behaviour, java vm runtime implementation
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