SNADS - SNA Distribution Services Overview
This document provides a basic SNADS overview.
Resolving the problem
Systems Network Architecture Distribution Services (SNADS) is an asynchronous distribution service that can store data for delayed or immediate delivery. SNADS serves as an operating system application that uses Advanced Program-To-Program Communications (APPC) to communicate with other systems in a SNADS network. APPC is the data communications support that allows programs on an OS/400 or i5/OS system to communicate with programs on other systems having compatible communications support. Because IBM Advanced Peer-to-Peer Networking (APPN) support is an extension of APPC, data can be routed by SNADS through an APPN Network.
SNADS provides the routing, sending, and receiving operations, allowing users to exchange distributions containing messages, data, documents, files and input streams with other users in the SNADS network. SNADS uses a system distribution directory to direct distributions to users in a local system or to other systems in a SNADS network. The SNADS routing function runs in the AnyMail/400 Mail Server Framework (MSF) which will be briefly addressed later in this document.
In layman's terms - SNADS allows users to send spooled files, save files, physical files, messages, documents and other objects to a remote system over an APPC connection.
IBM has grouped many of the jobs and processes that control the functions of the SNADS network in the QSNADS subsystem. Therefore, the QSNADS subsystem must be active for SNADS to work as designed. IBM-supplied transaction programs, such as Document Interchange and Object Distribution, also run in the QSNADS subsystem. The following processes run in the QSNADS subsystem:
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The QZDSTART process (job) starts the other SNADS processes when the QSNADS subsystem is started. When you end the QSNADS subsystem, the QSNADS job queue is cleared. Therefore, user should not use the QSNADS job queue to submit jobs unrelated to SNADS. The QZDSTART process also releases any distribution queues that were previously in the error-held state.
The sender process (job) names match the name of the APPC remote location (RMTLOCNAME) defined for a distribution queue. There is one sender process for each *SNADS entry in the distribution queue table. In other words, there will be at least one sender job under the subsystem QSNADS for every distribution queue of type *SNADS, and this sender job name will be the Remote Location Name parameter specified in the queue description. Therefore, each sender job sends the distributions of its own SNADS queue.
The receiver processes (jobs) can run in the QSNADS subsystem (or any other subsystem in which they are configured). The Add Communications Entry (ADDCMNE) command is used to configure a subsystem to operate with a communications device. A prompt from a remote sender starts the receiver process, which then receives distributions from other systems. The IBM-supplied QCMN subsystem typically contains the default entries that support receiver jobs.
The QMSF process (job) provides the routing function for SNADS. SNADS uses an API function of the Mail Server Framework (MSF) to determine the correct route for a distribution. In the route determination process, SNADS accesses the system distribution directory, the SNADS routing table, the SNADS distribution queue list, the SNADS secondary system name table and through an MSF API determines the correct route of a particular distribution. However, because the QMSF is not exclusively used by SNADS, it is not part of the QSNADS subsystem. This job is shipped as part of the IBM-supplied subsystem QSYSWRK. There is an autostart entry, QZMFECOX, that is shipped as part of the QSYSWRK subsystem and is responsible for automatically starting one QMSF job when subsystem QSYSWRK is started. Therefore, a QMSF job must be running under subsystem QSYSWRK for SNADS to work as designed.
Program processes such as document interchange (QDIA) and object distribution (QNFTP) handle distributions delivered to local users. The QDIALOCAl process (job) is used to do asynchronous processing if you have IBM OfficeVision installed. The indirect user mail controller process QDIAINDUSR is also included. This process removes mail from the queue for indirect users who are identified as such in the system directory and prints the mail with an attached cover page.
More support for:
Software version: Version Independent
Operating system(s): IBM i
Reference #: N1019696
Modified date: 21 February 2013
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