System Configuration

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# 2. System Configuration

We will assume the two QNX computers are called `A` and `B`. The system configuration is shown in the diagram below:

Figure 9. System Configuration.

Computer `A` is running a Cascade DataHub which has been given the domain name `a` by starting it using the following command:

        datahub -d a

Computer `B` is running a Cascade DataHub, which has been given the domain name `b` by starting it as:

        datahub -d b

The InTouch computer is called computer `C`. If you have more than one InTouch computer, then you would need to duplicate the following procedure for each InTouch computer. Computer `C` is linked to both QNX computers via a TCP/IP network and receives data from QNX by using Cascade Connect.

There are two Cascade Connect programs running on computer `C`, one to connect to each QNX computer that will be transmitting data to InTouch. The InTouch display screens have been configured to show data from either datahub `a` or datahub `b` by using InTouch scripts to create what are called "Indirect" tags. The InTouch configuration is described later in this document.

Cascade Connect automatically sends a message to the Windows Client program every time the link to a Cascade DataHub is broken or established. It is this `db_`datahub name`_up` message from Cascade Connect that triggers InTouch to switch from one datahub connection to the other. The switchover is very fast and completely transparent to the user.

| This document assumes that you have installed and fully tested the Cascade Connect software. The Cascade Connect configuration settings described in this document are the main settings that need to be configured for hot standby to work with InTouch. There are additional settings for Cascade Connect that may need to be configured for your particular application. If you need assistance please read the Windows Help file, the Cascade Connect User Manual, or contact `<support@cogent.ca>`.

| InTouch uses the name "tags" to describe data points so we will use this name in our discussion and examples.

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