RHEL has automatic tmp file cleanup mechanism
( RHEL 5-6 -> /etc/cron.daily/tmpwatch / RHEL 7 -> tmpfiles.d ) 

Oracle RAC creates socket files under /tmp/.oracle and /var/tmp/.oracle

If RHEL tmp file cleanup cleans RAC needed files, RAC crashes.
Therefore, solution is excluding these folders from cleanup.
RHEL-7 solution is below

[server1]/#tail -2 /etc/tmpfiles.d/tmp.conf
x /tmp/.oracle/
x /var/tmp/.oracle/
[server1]/usr/lib#