Using System State Manager › Define Prerequisite Resources › Define Positive and Negative Subrequisite Resources

Define Positive and Negative Subrequisite Resources

The positive and negative subrequisite capability is the equivalent of the positive and negative prerequisite capability described above.

To define positive and negative subrequisite resources

1. You can qualify the resources in a prerequisite list as a positive or negative subrequisite by adding a less than (<) or a greater than (>) sign before its name.
   • A positive subrequisite is considered to be satisfied when the resource with the subrequisite is DOWN.
   • A negative subrequisite is considered to be satisfied when the resource with the subrequisite is UP.

Notes:

• Resources in a prerequisite list that have been prefixed with a less than or greater than character are never evaluated as prerequisites. They are only evaluated as a subrequisite to the resource in the NAME column.
• To avoid over complexity, the positive and negative subrequisite capability can not be utilized within a MINOF statement.

Example: Positive and Negative Subrequisite Resources Definitions

Suppose that you are managing two resources; TASK1 and TASK2. Although you are not concerned in which order they start, you want to make sure that TASK2 is always stopped before TASK1. This is an example of when a positive subrequisite would be useful. The table would look like this:

NAME     DESIRED_STATE   CURRENT_STATE   PREREQ
TASK1     UP             UP
TASK2     UP             UP              >TASK1

In this table, TASK1 is listed as a positive subrequisite for TASK2. When System State Manager goes to start TASK2, it ignores the >TASK1 value in the PREREQ column. Furthermore, TASK1's definition as a positive subrequisite for TASK2 has no influence on System State Manager's starting process for TASK1.

The result is that either resource can be started first. However, any attempt to stop TASK1 first before stopping TASK2 will fail because TASK1 is a subrequisite for TASK2.

In a variation of this example, suppose you are not concerned in which order they start, but you wanted to make sure TASK1 could only be stopped when TASK2 was UP. This could be achieved by making TASK1 a negative subrequisite for TASK2:

NAME      DESIRED_STATE    CURRENT_STATE    PREREQ
TASK1      DOWN             DOWN
TASK2      UP               UP               <TASK1

In this table, TASK1 is listed as a negative subrequisite for TASK2. When System State Manager goes to start TASK2, it ignores the <TASK1 value in the PREREQ column. Furthermore, TASK1's definition as a negative subrequisite for TASK2 has no influence on System State Manager's starting process for TASK1. However, any attempt to stop TASK1 will only be honored if TASK2 is UP. Attempts to stop TASK1 will fail if TASK2 is already DOWN.