By default, Couchbase Server will send clients a temporary out of memory error if RAM is 95% consumed and only 5% RAM remains for overhead. We do not suggest you change this default to a higher value; however you may choose to reduce this value if you think you need more RAM available for system overhead such as disk queue or for server data structures. To change this value:
>./cbepctl 10.5.2.31:11210 -b bucket_name -p bucket_password set flush_param mutation_mem_threshold 65
Be aware that this tool is a per-node, per-bucket operation. That means that if you want to perform this operation, you must specify the IP address of a node in the cluster and a named bucket. If you do not provided a named bucket, the server will apply the setting to any default bucket that exists at the specified node. If you want to perform this operation for an entire cluster, you will need to perform the command for every node/bucket combination that exists for that cluster.
In this example we reduce the threshold to 65% of RAM. This setting must be updated on a per-node, per-bucket basis, meaning you need to provide the specific node and named bucket to update this setting. To update it for an entire cluster, you will need to issue the command for every combination of node and named bucket that exists in the cluster.