The log file for RCP8, and some of the IRIS log file such iris_out 
in the /usr/iris_data/log are no longer used for logging the stdout, and stderr on CentOS 7.
All logging information for these 2 daemons, and others that is using systemd
are directed to the system syslog. To read the system syslog you have to use a tool called journalctl. 
To get more information about journalctl, please consult with the man page (man journalctl).  

Note:  To read the syslog you have to login as root user.

To read the logging information for RCP8
# journalctl –u rcp8.service 

To read the logging information for IRIS:
# journalctl –u iris.service 

You can also check the status of the service by running "systemctl status <service name>". For more information about systemctl,
consult the man page (man systemctl).
For example, to check if the rcp8 service is started OK, or failed, run

#systemctl status rcp8.service

