You may reach the maximum number of clients that are allowed to connect to your Apache web server and Apache stops responding. In this case, you have to increase the MaxClients and ServerLimit variable to a higher value.
The changes has to be placed in the Apache configuration file located at /usr/local/apache/conf/httpd.conf but in case of Apache 2.x version or higher, you may not be able to save the changes directly and a restart of Apache service will reset the values of the two directives.
You may receive the following warning message on restarting the Apache web service:
WARNING: MaxClients of 500 exceeds ServerLimit value of 256 servers, lowering MaxClients to 256. To increase, please see the ServerLimit directive.
In order to overcome the error, you need to execute the following two commands to make the changes permanent.
/usr/local/cpanel/bin/apache_conf_distiller –update –main
This will also prevent any changes to overwrite on the next cPanel update.