Weblogic Terminology

• Domain: is a logically related group of WebLogic Server resources .A domain is an interrelated set of WebLogic Server resources that are managed as a unit.

• Administration Server: The server instance which configures, manages, and monitors all other server instances and resources in the domain. An Administration Server is a WebLogic Server instance that maintains configuration data for a domain.

• Managed Server: is a WebLogic Server instance that runs deployed applications.
• When a Managed Server starts up, it connects to the domain's Administration Server to synchronize its configuration document with the document that the Administration Server maintains.You can start a Managed Server even if the Administration Server is not running. In this case, the Managed Server uses a local copy of the domain’s configuration files for its starting configuration and then periodically attempts to connect with the Administration Server. When it does connect, it synchronizes its configuration state with that of the Administration Server.

•  If a Managed Server cannot connect to the Administration Server during start up, it can retrieve its configuration by reading its locally cached configuration data from the config directory.

• A Managed Server that starts in this way is running in Managed Server Independence (MSI) mode. By default, MSI mode is enabled.

• All Managed Servers in a cluster must reside in the same domain; you cannot split a cluster over multiple domains.
•  All Managed Servers in a domain must run the same version of the WebLogic Server software. The Administration Server may run either the same version as the Managed Servers in the domain, or a later service pack.
• Each Managed Server maintains a copy of the domain’s configuration files. This copy is read-only and can be updated only as part of a change management process.

•  When the Administration Server starts up, it saves a JAR file named config-booted.jar that contains the configuration files. When you make changes to the configuration files, the old files are saved in the configArchive directory under the domain directory, in a JAR file with a sequentially-numbered name like config-1.jar.
• Configuration changes that can take effect without a server restart are sometimes referred to as dynamic changes.

           Ex: if you change a Managed Server’s Listen Port value, the new port will not be used until the next time you start the Managed Server. The updated value is stored in config.xml, but the run time value is not affected.

• configuration changes that require a server restart are sometimes referred to as non-dynamic changes
• We can't start the server when it is in ADMIN mode, we can Resume the server to start.
• We can Shutdown the server which is in ADMIN Mode.
• The Administration Console is a browser-based Web application that allows you to configure and monitor your WebLogic Server domain, server instances, and running applications and their associated resources. You can also use the Administration Console to create new server instances and clusters and tune application descriptors