IBM Tivoli NetView for z/OS Programming: Pipes - IBM notice

stages have a third stream, which is called the tertiary stream. Streams 4 through
10 are referred to only by their stream numbers.
There are two additional data stream terms to understand:
Defined
A data stream is defined when the pipeline specification calls for data to
flow between two stages. For example, the following pipeline displays HI
THERE on the console:
PIPE LITERAL /HI THERE/
|CONSOLE
In this case, the CONSOLE stage has one input and no output stream
defined. The input is from the LITERAL /HI THERE/ stage. In stages that do
not allow multiple input and output streams, the position of the stage
within the pipeline specification defines how the data will flow to and
from the stage.
The primary input and output streams are usually defined by the position
of the stage specification within the pipe specification. The primary input,
if required, is usually from the previous stage within the pipe specification.
The primary output is usually to the following stage within the pipe
specification, unless the stage is the last stage within the pipeline
specification. In the latter case, the primary output differs depending on
the individual stage.
Streams, other than the primary input and primary output, are defined
using labels. For information on labels and complex pipelines, see
“Complex Pipelines” on page 7.
Connected
Data streams are connected and disconnected during the processing of the
pipeline. A data stream is connected until the stages connected to the data
stream disconnect. A stage will disconnect when a condition, specific to the
stage, is encountered. Most stages retain their connections until they
terminate. When a stage disconnects its output stream, the corresponding
input stream will disconnect as soon as any messages being passed
through the stream have been read in, or consumed, by the partner stage.
For example, in Figure 7, Stage A and Stage B are connected by a data
stream. The output stream of Stage A is the input stream of Stage B. Stage
A completes processing and disconnects. Only after Stage B completes
reading any messages sent from Stage A does the data stream itself
disconnect.
Output Input
Data
Stage A Stage B
Stream
Figure 7. Input and Output Data Streams
Introduction and Concepts
Note: Defined is the state of the stream as coded in the pipeline specification and
connected is the status of the stream during pipeline processing.
Chapter 1. NetView Pipelines Introduction and General Concepts 5