(Errcode: 24 - Too many open files) (23)
에러 처리용
DB서버에서 실행
# ulimit -n 20480
# vi /etc/security/limits.conf
* hard nofile 30720
* soft nofile 20480
root hard nofile 30720
root soft nofile 20480
mysql hard nofile 30720
mysql soft nofile 20480
# vi /etc/systemd/system/mysql.service
LimitNOFILE=20480
# systemctl daemon-reload
# systemctl restart mysql.service