*Back to [[Book|Administrator's Configuration File Reference#cfr]] [[Topic|Administrator's Configuration File Reference#chap1]]*
h2. Dynamic Reconfiguration
Dynamic reconfiguration allows you to make configuration changes to a runtime Web Server. You do not have to stop or restart the Web Server for the changes to take effect.
Dynamic configuration happens in one of the following ways:
* When you deploy a configuration through the Admin Console or CLI
* When you run the {{reconfig}} script in the server instance's {{bin}} directory
You can dynamically change the configuration settings in the {{obj.conf}}, {{mime.types}}, and ACL files without restarting the server. In addition, most settings in the {{server.xml}} file can be changed without restarting the server. If a server restart is required, a warning message appears in the server log when you deploy the configuration or run the {{reconfig}} command.
You cannot dynamically reconfigure the following {{server.xml}} configuration parameters:
* {{user}}
* {{temp-path}}
* {{log}} (with the exception of log-level)
* {{thread-pool}}
* {{pkcs11}}
* {{stats}}
* {{cgi}}
* {{dns}}
* {{dns-cache}}
* {{file-cache}}
* {{acl-cache}}
* {{ssl-session-cache}}
* {{access-log-buffer}}
* {{jvm}} (with exception of log-level)
When you run the {{reconfig}} command, a new configuration object is created and all new incoming requests are processed based on this new configuration object. The current configuration object gets removed when no HTTP requests are using the object. For example, if you are using Web Server with reverse proxy in the front-end can dynamically add a new back-end server and apply the reconfiguration by using the {{reconfig}} command.
The following additional configuration changes within {{server.xml}} are supported by the {{reconfig}} command:
* Add a new HTTP listener
* Add a new Java web application
{info:title=Note -}If the web application requires changes to the JVM or require a new JDBC resource, then you must restart the server instead of using the {{reconfig}} command.
{info}
{info:title=Note -}Some configuration changes cannot be instantly propagated to the running server. For example, adding a JVM property of a resource.
{info}
If a misconfiguration occurs during dynamic reconfiguration, the server displays an error message. The server logs the error message to a log file specified by the previous known good configuration.
Certain misconfigurations result in warning messages but do not cause the server to reject the configuration. Other misconfigurations result in error messages and cause the server to reject the configuration. If the server rejects a configuration during startup, the server does not start. If the server rejects a configuration during dynamic reconfiguration, the server reverts to the previous known good configuration.
h2. Dynamic Reconfiguration
Dynamic reconfiguration allows you to make configuration changes to a runtime Web Server. You do not have to stop or restart the Web Server for the changes to take effect.
Dynamic configuration happens in one of the following ways:
* When you deploy a configuration through the Admin Console or CLI
* When you run the {{reconfig}} script in the server instance's {{bin}} directory
You can dynamically change the configuration settings in the {{obj.conf}}, {{mime.types}}, and ACL files without restarting the server. In addition, most settings in the {{server.xml}} file can be changed without restarting the server. If a server restart is required, a warning message appears in the server log when you deploy the configuration or run the {{reconfig}} command.
You cannot dynamically reconfigure the following {{server.xml}} configuration parameters:
* {{user}}
* {{temp-path}}
* {{log}} (with the exception of log-level)
* {{thread-pool}}
* {{pkcs11}}
* {{stats}}
* {{cgi}}
* {{dns}}
* {{dns-cache}}
* {{file-cache}}
* {{acl-cache}}
* {{ssl-session-cache}}
* {{access-log-buffer}}
* {{jvm}} (with exception of log-level)
When you run the {{reconfig}} command, a new configuration object is created and all new incoming requests are processed based on this new configuration object. The current configuration object gets removed when no HTTP requests are using the object. For example, if you are using Web Server with reverse proxy in the front-end can dynamically add a new back-end server and apply the reconfiguration by using the {{reconfig}} command.
The following additional configuration changes within {{server.xml}} are supported by the {{reconfig}} command:
* Add a new HTTP listener
* Add a new Java web application
{info:title=Note -}If the web application requires changes to the JVM or require a new JDBC resource, then you must restart the server instead of using the {{reconfig}} command.
{info}
{info:title=Note -}Some configuration changes cannot be instantly propagated to the running server. For example, adding a JVM property of a resource.
{info}
If a misconfiguration occurs during dynamic reconfiguration, the server displays an error message. The server logs the error message to a log file specified by the previous known good configuration.
Certain misconfigurations result in warning messages but do not cause the server to reject the configuration. Other misconfigurations result in error messages and cause the server to reject the configuration. If the server rejects a configuration during startup, the server does not start. If the server rejects a configuration during dynamic reconfiguration, the server reverts to the previous known good configuration.