Discovery Knowledge Scripts allow you to specify the type of discovery you want to perform when a discovery job runs. You can specify a full discovery or a delta discovery. A full discovery performs a complete discovery of all information and sends this information to the QDB each time the discovery job runs. A delta discovery identifies any changes since the last discovery job and only sends changes to the QDB.
Delta discoveries are more efficient and require fewer system and network resources to perform since they only send information about changes to the QDB. This is the default setting for any new discovery job you run. However, the first time you run a delta discovery job it will perform a full discovery since there is no previous full discovery to compare against. Any subsequent jobs will perform a delta discovery.
It is possible to have a delta discovery job running at the same time as a full discovery job. For example, you might have a delta discovery job that runs daily and a full discovery job that runs weekly. If these two jobs run concurrently, when the agent compares the full discovery to the delta discovery it might not detect any changes since the full discovery includes the same information as the delta discovery. To avoid this error, the agent drops the delta discovery job and only uses the full discovery. This ensures that the job discovers all changes. For more information about delta discovery, see the Help.
Due to the nature of clustered resources that you monitor with AppManager, you cannot use delta discovery with these resources. This includes discovery of clustered servers and SQL and Exchange installed on clustered servers. Attempting to perform delta discovery on these clustered resources will result in discovery errors, including missing or repeated discovery information. To avoid this problem, configure any discovery Knowledge Scripts you run on clustered resources to perform a full discovery with each discovery. While you might not see the same performance improvements available with delta discovery, this method ensures there are no discovery errors with clustered resources.
AppManager never deletes top-level objects in the Enterprise Layout view of the Navigation pane as the result of a discovery. For example, if you perform a delta discovery for servers in your environment and one or more servers happen to be unavailable when you run the discovery, these servers appear as deleted servers in the delta discovery results. However, the servers are not actually gone, they are simply unavailable. To remove a discovered top-level object from the Enterprise Layout view, you must manually delete it. This ensures AppManager does not inadvertently delete objects as the result of a discovery.
Unlike top-level objects, AppManager does delete sub-objects, such as printers, from the Enterprise Layout view as the result of delta discovery.
If you manually delete a top-level object from the Enterprise Layout view, subsequent delta discoveries will not re-discover the deleted object and restore it to the view. To restore top-level objects that you manually delete, perform a full discovery.
If a previously deleted sub-object is physically restored to your monitored environment, a delta discovery automatically restores it to the Enterprise Layout view.