Rules

Rules in a chain describe the way the Scheduler should read the job description. A chain must have a proper starting point and end point. Steps in a chain are activated when the rules in the chain definition evaluate to true (as rules are Boolean) and mention the specific step names to be started.

Let's return to the backup example once more. We know there is only one location where it makes sense to start the job—the step that shuts down the database. How can we make the Scheduler know that? Let's start with an overview of what we know. The steps are:

1. 1. Always start with SHUTDOWN.

2. 2. If SHUTDOWN is successful, start COPYFILES.

3. 3. If COPYFILES is successful, start STARTUP.

4. 4. If STARTUP is successful, start END 0.

   This lists the optimum order of executions, but does not take into account a situation with failures. What should we do if SHUTDOWN fails? What should we do if COPYFILES fails? What should we do if STARTUP fails? If it is important that we act on a status, we should tell this...