This is only relevant if you are running Snow Owl with an embedded Elasticsearch and not connecting it to an existing cluster.
Snow Owl (with embedded Elasticsearch) uses a lot of file descriptors or file handles. Running out of file descriptors can be disastrous and will most probably lead to data loss. Make sure to increase the limit on the number of open files descriptors for the user running Snow Owl to 65,536 or higher.
For the .zip and .tar.gz packages, set ulimit -n 65536 as root before starting Snow Owl, or set nofile to 65536 in /etc/security/limits.conf.
RPM and Debian packages already default the maximum number of file descriptors to 65536 and do not require further configuration.