The appropriate size for a Context Store deployment is based on the following variables:
The average size of context objects created
The average lease time of the created context objects
The rate at which new context objects are being created
The inclusion of additional Context Store features, such as External Data Mart, geo-redundancy, high availability, Context Store Event Streams , Audit Trail, and aliasIds, which themselves have memory requirements.
The Context Store Release Notes, available on Avaya Support site, contains the ContextStoreManager attribute configurations for 13 certified deployments of varying sizes; from a single-node with 8 GB of memory up to a cluster of three nodes with 128 GB of memory each.
You can also download a Capacity Planner Tool that assists you with custom sizing, from http://www.avaya.com/devconnect. This tool accepts inputs for the four variables and provides the best-estimate recommendations