At status my memory usage showing as 850/900.
How can I increase my memory for elasticsearch.
The heap size can be set with the ES_HEAP_SIZE environment variable. If you're starting Elasticsearch as a service you should probably be changing /etc/sysconfig/elasticsearch (RPM-based systems) or /etc/default/elasticsearch (Debian-based systems).
https://www.elastic.co/guide/en/elasticsearch/reference/current/setup-configuration.html