Logical Problem Determination for SNA Networks

Problem determination on a Systems Network Architecture network has dealt mostly with error detection on physical network components. Adequate logical error-detection mechanisms associated with the logical network (software-related) errors have been only recently provided with the announcement of a new on-line interactive package called the Network Logical Data Manager (NLDM). This paper discusses the physical and logical network environments, logical network problems , and functions provided by the two releases of NLDM for logical problem determination. S ystems Network Architecture (SNA)' can be viewed as consisting of two networks, a physical one and a logical one. The physical network is made up of a number of hardware nodes interconnected by links. The function of the physical network is to control the flow of user data to, from, and between the physical network nodes. The logical network consists of the management of protocols that support the exchange of user data. Although these two networks can be viewed separately, they interact closely since the logical network operates via the physical network. In the past, problem determination has mostly dealt with the physical network. Error-reporting and error-recording mechanisms evolved from stand-alone diagnostic support on individual hardware nodes to on-line interactive diagnostic support of remote hardware nodes. Such IBM program products as the Network Problem Determination Application (NPDA)* have been developed that allow an SNA user either to receive alerts from the network nodes of pending or failed conditions or to query network nodes and intelligent modems3 for status data. SNA network logical problem determination capabilities have not evolved as rapidly. Until the announcement of the Network Logical Data Manager (NLDM),4 the logical problem determination mechanisms were considered cumbersome and time-consuming. NLDM was created to provide on-line support that enables the user, normally the network operator or trained diagnostician, to interactively display data about the logical S N A network for problem determination purposes. NLDM constantly collects and maintains status information about the SNA network. This information is presented in the context of logical conversations, called sessions in SNA, such that information is available leading up to the occurrence of a failure. The initial release of NLDM collects and displays session awareness and trace information about the session end points. The second release' expands this visibility to the network routes that are traversed by the sessions. Also included is support for the SNA Network Intercon-nectiod environment. This paper first describes in more detail the …