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

Introduction and Concepts
Pipeline Stages
2 Programming: Pipes
Imagine a stage as a small black box inserted into the plumbing pipeline described
in Table 1 on page 1. Also, imagine a series of such boxes, all connected serially,
one after the other, throughout the length of the pipeline. Furthermore, imagine
that each box performs one specific task on the water passing through it: adjust
temperature, remove salt, or add chlorine. Even though each box does only one
thing, the cumulative result is salt-free, temperature-controlled, chlorinated water.
Something similar happens in a NetView pipeline: data passes through a stage
which performs some action on the data. In Figure 1 you can see several stages
linked together to form a pipeline that takes data from a disk, processes it, and
displays it on an operator console.
Disk
File
Stage
1
Figure 1. Stages within a Pipeline
Stage
2
Stage
3
Bit
Bucket
Data in the pipeline is viewed as a series of discrete records called messages. They
are so called because, when read into the pipeline, each record becomes a message
consisting of message text and message attributes.
Figure 2 shows an example of a stage processing messages. Unprocessed messages
enter from the left, the stage reads and processes them, and the output appears on
the right. This is analogous to the operation of one black box in our earlier
plumbing metaphor. Just as in the earlier metaphor, you can string together several
stages, each one driven by the output of a preceding stage and each one
performing some unique operation on your data.
Input Message 1
Input Message 2
Input Message 3
Stage
Figure 2. Messages Flowing through a Stage
Output Message 1
Output Message 2
In this example, practically anything can happen to the messages: they can be
modified, discarded, split apart, joined together, and so on. Precisely what happens
depends on the stage that is being used. Many stages generate one output message
for each input message; some commands do not. In this example, three messages