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Target

The term 'target' refers to an entity that is managed via Enterprise Manager Grid Control. Target is the most important entity in Enterprise Manager Grid Control. All other processes and subsystems revolve around the target subsystem. For each target there is a model of the target that is saved in the Enterprise Manager Repository. In this article, we will use the terms target and target model interchangeably.

Major building blocks of the target subsystem are:

Target definition:

All targets are organized into different categories, just like the actual entity that they represent, for example there is WebLogic Server target, Oracle Database target, and so on. These categories are called target types.

For each target type there is a definition in XML format that is available with the agent as well as with the repository. This definition includes:

• Target Attributes: There are some attributes that are common across all target types, and there are some attributes specific to a particular target type. The example of a common attribute is the target name, which uniquely identifies a managed entity. The example of a target type specific attribute is the name of a WebLogic Domain for a WebLogic Server target. Some of the attributes provide connection details for connecting to the monitored entity, such as the WebLogic Domain host and port. Some other attributes contain authentication information to authenticate and connect to the monitored entity.
• Target asociations: Target type definition includes the association between related targets, for example an OC4J target will have its association defined with a corresponding Oracle Application Server.
• Target Metrics: This includes all the metrics that need to be collected for a given target and the source for those metrics. We'll cover this in greater detail in the Metrics subsystem.

Every target that is managed through the EM belongs to one, and only one, target type category. For any new entity that needs to be managed by the Enterprise Manager, an instance of appropriate target type is created and persisted in the repository.

Out-of-the-box Enterprise Manager provides the definition for most common target types such as the Host, Oracle Database, Oracle WebLogic Server, Seibel suite, SQLServer, SAP, .NET platform, IBM Websphere application server, Jboss application server, MQSeries, and so on. For a complete list of out-of-the-box targetsOut-of-the-box Enterprise Manager provides the definition for most common target types such as the Host, Oracle Database, Oracle WebLogic Server, Seibel suite, SQLServer, SAP, .NET platform, IBM Websphere application server, Jboss application server, MQSeries, and so on.For a complete list of out-of-the-box targets please refer to the Oracle website.

Now that we have a good idea about the target definition, it's time we get to know more about the target lifecycle.

Target lifecycle

As the target is very central to the Enterprise Manager—it's very important that we understand each stage in the target life cycle.

Please note that not all the stages of the lifecycle may be needed for each target. However, to proceed further we need to understand each step in the target lifecycle. Enterprise Manager automates many of these stages, so in a real life scenario many of these steps may be transparent to the user. For example, Discovery and Configuration for monitoring stages are completely automated for the Oracle Application Server.

Discovery of a target

Discovery is the first step in the target lifecycle. Discovery is a process that finds the entities that need to be managed, builds the required target model for those entities, and persists the model in the management repository. For example, the discovery process executed on a Linux server learns that there are OC4J containers on that server, it builds target models for the OC4Js and the Linux server, and it persists the target models in the repository.

The agent has various discovery scripts and those scripts are used to identify various target types. Besides discovery, these scripts build a model for the discovered target and fill in all of the attributes for that target. We learnt about target attributes in the previous section.

Some discovery scripts are executed automatically as a part of the agent installation and therefore, no user inputs are needed for discovery. For example, a discovery script for the Oracle Application Server is automatically triggered when an agent is installed. On the other hand, there are some discovery scripts where the user needs to provide some input parameters. An example for this is the WebLogic server, where the user needs to provide the port number of the WebLogic Administration Server and credentials to authenticate and connect to it. The Enterprise Manager console provides interface for such discovery.

Discovery of targets can happen in two modes—local mode and remote mode. In local mode, the agent is running locally on the same host as the target. In remote discovery mode, the agent can be running on a different host. All of the targets can be discovered in local mode and there are some targets that can be discovered in remote mode. For example, discovery of WebLogic servers can happen in local as well as remote mode.

One important point to note is that the agent that discovered the target does the monitoring of that target. For example, if a WebLogic Server target is discovered through a remote agent it gets monitored through that same remote agent.

Configuration for monitoring

After discovery the target needs to be configured for monitoring. The user will need to provide some parameters for the agent to use to connect to the target and get the metrics. These parameters include monitoring credentials, host, and port information, using which, the agent can connect to the target to fetch the metrics. The Enterprise Manager uses these parameters to connect, authenticate, and collect metrics from the targets. For example, to monitor an Oracle database the end user needs to provide the user ID and password, which can be used for authentication when collecting performance metrics using SNMP protocol.

Enterprise Manager Console provides an interface for configuring these parameters.

For some targets such as Application server, this step is not needed, as all the metrics can be fetched anonymously. For some other targets such as Oracle BPEL Process Manager, this step is needed only for detailed metrics; basic metrics are available without any monitoring configuration, but for advanced metrics monitoring, credentials needs to be provided by the end user. In this case, monitoring credentials are the user ID and password, used to authenticate when connecting to BPEL Process Manager for collecting performance metrics.

Updates to a target

Over a period of time, some target properties, attributes, and associations with other targets change—the EM target model that represents the target should be updated to reflect the changes. It is very important that end-users see the correct model from Enterprise Manager to ensure that all targets are monitored correctly. For example, in a given WebLogic Cluster, if a new WebLogic Server is added and an existing WebLogic Server is removed—Enterprise Manager's target model needs to reflect that. Or, if credentials to connect to WebLogic Admin Server are changed—the target model should be updated with new credentials. The Enterprise Manager console provides UI interface to update such properties.

If the target model is not updated there is a risk that some entity may not be monitored, for example if a new WebLogic server is added but the target model of domain is not updated, the new WebLogic server will not be monitored.

Stopping monitoring of a target

Each IT resource has some maintenance window or planned 'down-time'. During such time it's desirable to stop monitoring a target and collecting metrics for that resource. This can be achieved by putting that target into a blackout state. In a blackout state, agents do not collect monitoring data for a target and they do not generate alerts. After the maintenance activity is over, the blackout can be cleared from a target and routine monitoring can start again. Enterprise Manager Console provides an interface for creating and removing blackout state for one or more targets.