Deploying SNA Server to provide host connectivity for desktops and server PCs offers many advantages, including: flexibility to perform multiple functions; efficient use of host resources; support for a virtual LAN over SNA-only data links; flexible network administration; broad support for required SNA applications; and integration of BackOffice-based applications with host data.
SNA Server performs multiple functions that help the network integratedisparate desktop, LAN, and host systems.
Figure 2.12 SOGA relies on flexible SNA gateway solutions such as SNA Server. SNA Server has broad support for multiple desktop operating systems and popular LAN protocols.
An SNA gateway approach allows the host to be configured with only native SNA. The workstations can be configured with only TCP/IP or another popular LAN protocol. The SNA gateway approach allows PU-sharing, reducing the number of PUs required on the host; therefore, the host only needs to poll the SNA gateway. With other host-access models, hundreds of end-user definitions are typically stored in resident memory on the host system and FEP, consuming expensive host resources. By assigning host sessions to individual user accounts on the SNA gateway machine, SNA gateways save memory and CPU cycles on the host system.
Another option with SNA Server is the capability of creating a virtual LAN over SNA-only host links. This option is most often used in traditional branch-based configurations where no WAN exists between remote sites. Remote offices can be linked together across APPC LU6.2 connections established between SNA Server computers. The feature is called SNA Remote Access Service. The effect is to create a slow-link WAN that interconnects otherwise isolated branch-office LANs. This solution is ideal for providing communication between other Microsoft BackOffice or Windows NT Server-based applications that would be isolated in an SNA-only WAN environment. For example, post office-to-post office communications between remote Microsoft Exchange Server computers can be accomplished using SNA Remote Access Service.
When all host-bound traffic is concentrated through SNA Server, the network manager can use performance-monitoring, event-logging, and tracing capabilities of the Windows NT Server platform more effectively to manage desktop-to-host traffic. An individual desktop problem is easy to work around by simply assigning a new LU while the administrator performs debugging at the server without interrupting other users or restarting the server.
Even though SNA Server provides the capability for greater server-based network management, it is not uncommon for large enterprises to perform all or most of their network management on IBM mainframe systems, using tools such as IBM NetView. SNA Server supports NetView to make centralized network management simpler.
SNA Server can forward to NetView custom alerts and informational messages from any Windows NT Server in the domain, using an optional NVAlert service. All events logged to the Windows NT Event Log can be viewed by the host NetView console operator. This allows for central monitoring of distributed server-based solutions.
Yet, the SNA Server NVAlert service only informs the NetView console operator of the problem. It does little good to know of a problem if one cannot act on the information. This is why SNA Server installs a NetView RunCmd service on the Windows NT Server computer, which extends access to the Windows NT command line for the host NetView console operator. The NetView RunCmd service allows the NetView console operator to directly control all functions of the Windows NT Server on which SNA Server is running.
SNA Server uses industry-standard SNA protocols for connecting to IBM mainframe and AS/400 computers. This allows host systems to run the native SNA protocols for which they have been optimized. At the same time, SNA Server supports client emulators and server-based APPC applications across all popular LAN protocols, including TCP/IP, IPX/SPX, Banyan VINES, and Microsoft Networking. This allows desktop and server computers to run the protocol that has been chosen by the network manager. With SNA Server, network managers can immediately begin to integrate their disparate systems, while planning their next-generation information solutions.
Figure 2.13 SNA Server's client/server architecture provides support for the required SNA APIs on popular client platforms and the Windows NT Server operating system.
SNA Server is designed using a client/server model. On every client computer there is an SNA Server module that provides support for a full range of application programming interfaces and allows for the protocol-neutral LAN connection. On the SNA Server computer there are the same broad range of APIs for basing server-to-host solutions. See Figure 2.13 for a view of the SNA Server client/server architecture.
Based on the Windows NT Server operating system platform, a channel-attached SNA Server computer can also be shared with other functions, such as file and print server, e-mail server, database server, systems management server, and Internet or intranet server. Because SNA Server is an integrated part of Microsoft BackOffice, it acts as glue to bond BackOffice applications and services with host systems and data.
Multiple SNA Server computers linked using SNA Remote Access Service allow Windows NT Server computers to share files and security validation information.
SNA Server supports Windows NT Server another way through its NetView Services, which allow host administrators to execute any Windows NT command line from an IBM NetView console. Other capabilities of this feature set make it possible to forward any Windows NT event log message to NetView and permit LAN administrators to view NetView performance data on any Windows NT Performance Monitor. NetView Services allow organizations to integrate Windows NT Server-solutions, such as SNA Server, into their existing NetView centralized network management systems.
SNA Server ships with a copy of a StarSQL ODBC-to-DRDA™ driver. This driver allows the SNA Server Manager to integrate host data (DB2® for MVS, DB2 for VM, DB2/400 for OS/400) with Microsoft SQL Server™. Organizations no longer need to license and deploy expensive, single-purpose SQL-to-host database gateways to connect host databases with desktops and servers. Using ODBC-enabled tools such as Microsoft Query, data manipulation and presentation can be performed on the desktop with popular applications such as Microsoft Excel.
For truly mission-critical solutions, third-party products that are based on SNA Server provide DB2-to-SQL Server data replication. The vendors currently supporting SNA Server-based solutions include: ExecuSoft, ShowCase, and DataMirror.
SNA Remote Access Service supports all functions of Microsoft Systems Management Server (SMS). This allows a network manager to use the SMS software distribution, remote control, and other management capabilities across an enterprise using only SNA host links, such as dedicated leased-line SDLC connections.
SNA Remote Access Service enables post office-to-post office connectivity over SNA networks. This allows organizations to deploy Microsoft Exchange in sites that would otherwise be cutoff from server-based corporate e-mail.
PROFS and SNADS gateways, specifically designed to function with SNA Server, link host e-mail and scheduling to Microsoft Exchange Server. This provides organizations with the capability to migrate legacy e-mail and scheduling users to the latest server-based messaging technologies.
The Microsoft Internet Information Server includes an Internet Database Connector that, teamed with the StarSQL ODBC/DRDA driver, can be used to create forms-oriented data links between IBM DB2 databases and the Internet or intranet. This allows organizations to publish secure, host-based data directly to their Web servers. Additionally, publishers can provide hyperlinks from Web pages to files that reside on IBM mainframes or AS/400s using SNA Server's FTP-to-AFTP gateway.