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Connection: If the property is applied at the connection, then the containers of Mapper jobs will be launched with the same memory for all the cubes semantic models (if not applied to the cubesemantic model).
Semantic model: If the property is applied at the semantic model and connection both, then the value set at the semantic model will be respected for that particular semantic model.
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The property value should be configured considering the highest expected cardinality in the cube semantic model for any dimension or distinct count measure.
Kyvos lab tested optimal settings: For a dimension/distinct count measure with a cardinality of 1 Billion, the property should be set to 25600 (25 GB).