When we want to connect an IBM z/OS with a Microsoft Windows Server for ETL process purposes, it is important to understand how the IBM Mainframe network resources are configured and how to link this particular information in to the Microsoft Windows Server.

In this post I would like to explain how to configure the SNA Manager Application that is installed with Microsoft Host Integration Server (HIS) as the main link service tool. We will also look at using the IP-DLC link service (SNAIP1 windows service) to communicate with the IBM mainframe.

Understanding the basics

IBM z/OS includes a communications server with multiprotocol networking. It provides the data stream transportation corridor between the external network and the customer business applications running on z/OS. It basically uses a combination of TCP/IP and System Network Architecture (SNA) functions.

Technically, once HIS is installed in the Windows server, it communicates with the Mainframe by establishing a TN3270 session using TCP protocol. IBM’s communications server will translate this TN3270 session to SNA protocol. The application connection will be completed by acquiring a Logical Unit (LU) on behalf of the TN3270 connection created by HIS. This way, an LU-LU session is established between the communications server and the HIS.

All of the IBM processes are performed under a Virtual Telecommunication Access Method (VTAM) platform which provides the SNA layer network communication stack to transport data between applications and the end client.

APPN and APPC

The most common network topology configuration is the Advanced Peer-to-Peer Networking (APPN) defined by the VTAM Control Point (CP).  Its capabilities are related to enroot data in a network between two or more LU’s that do not need to be directly connected. The APPN network is enhanced with the Advanced Program-to-Program Communication (APPC), which defines the rules of how programs exchange information. This protocol is known as SNA LU 6.2. In other words, APPN defines how APPC traffic gets from one point to another in a network regardless the network configuration.

Configuring the SNA Manager

Once the HIS 2006 application has been installed in the Windows Server successfully, we have to run and configure the SNA Manager program.  This tool is designed to streamline the process of creating and managing connections to data sources in the host environment.

Once we have started up the SNA Manager program, the first step is to create a Microsoft SNA connection from the console root. Once created, Open SubDomain and select the primary configuration server. Once primary configuration server is defined, adding a new link service is mandatory. Two sections have to be defined: “Link Services setup” and the “SNA Service”. 

In the Link Services setup (managed by the SNAP1 windows service), first define the address as the primary network node server (NNS), then define the actual network name and its Control Point name in the local APPN node section. Finally, confirm “Use dynamic PU definition” check box so that independent LUs will be defined dynamically. LU’s are controlled by a Physical Unit (PU) in each node of an SNA network.

With the required link service already set up, individual resource connections between the  HIS servers and host servers must be configured as well. This is achieved by configuring an SNA service connection.

There are three steps for each SNA server connection setup (Connections, Local APPC LUs and Remote APPC LUs):

1. In connections, define the name for the connection, specify SNAP1 as the link service and “peer system” as remote end type of host system. Typically leave the rest of the tabs by default.
2. For the Local LU definition (our server), enter an 8 character length LU Alias and LU name which will identify the local system to other components on the SNA network, and specify the actual Network Name. Leave the advanced tab with default values.
3. For the Remote LU definition (IBM side), enter the LU alias and LU name, the Network Name, and Uninterpreted LU Name. These values should be requested from the SNA Network administrator. Finally in the Options tab, check “support parallel sessions” to increase the number of available connections, define QPCSUPP within “Implicit Incoming mode” as the way the Remote APPC LU is partnered with the Local APPC LU, specify the required SNA security level and uncheck Enable Syncpoint check box unless you have a Local APPC LUs configured for SyncPoint support.

It is highly recommended to run and configure the Data Access tool as well, (created by the HIS installation), as it provides an excellent opportunity to test the database connection by using a Universal Data Link (UDL) file for OLE DB connections.

After setting up the Data Source connection and linking an active SNA server with an active SNA service connection, you should be able to successfully connect to the Mainframe.

If you have any questions or feedback about this post, please feel free to leave a comment below.