In a VTAM APPN network, what is a directed search?

To establish a session in an APPN network, the location of the partner resource must be known to VTAM. A directed search is used to locate a partner resource when VTAM has location information for the resource as the result of a previous search or if there is a central directory server in the network.

A directed search uses information stored in the directory services database of a network node server to direct the search to the location of the requested LU. A directed search is sent to the node recorded as the owner of the requested LU to verify the information. A directed search can be sent to a network node server from an end node and to an end node from a network node server. A directed search can also be sent from a network node to a central directory server when the network node does not have information about the location of the destination logical unit or following a failed search.

A directed search is originated by a network node server for the LUs it serves, by a central directory server as a result of a search request from a network node, or by an end node to its network node server.

A directed search is needed when a network node server or a central directory server receives a request for an LU for which it has a location stored in its database. The search is used to verify the information. A directed search is also used by a network node server to send a search request to a central directory server if the network node server has no information about the location of a requested resource. A directed search is used by an end node to request location information about a resource from the end node network node server.