This chapter presents detailed descriptions of advanced aspects of job scheduling using SCHEDULE . These features include:

• Resource variables: Resource variables are can be read . A variable can be read by a job to determine a resource action and can be modified by a job for future interaction. Variables can also be placed into a job's command list using preprocessor commands.
• Expanded variables: In addition to simple resource variables EnterpriseSCHEDULE supports a rich set of variable expressions that feature simple or complex math expressions, date expressions and character expressions. This extends the power of variables and allows for run time calculation of dates and other values.
• Pre-processor substitution: The commands in a job are run through a pre-processor searching for control instructions and variable replacement expressions before the job is created.

This section explains advanced job interaction and gives examples of how to gain even more control of your job runs. While initiates ( Section 2.1.7) and prerequisites ( Section 2.1.9) allow a full range of interactivity between jobs, the advanced techniques described below can add an extra degree of programmability to your job runs.

In a standard job interaction sequence, when all prerequisites are completed the job is run and then the initiate list is processed, executing connected jobs. However, suppose you want to suppress the job if another job is currently running? Maybe you want to limit the number of jobs that can access a resource like a database at the same time. Or maybe you want to be able to set a variable that shuts off a whole section of your job group or even the whole group when you see fit. This is where advanced job programming comes into the picture.

Unlike initiates and prerequisites, a job's general resource list is not connected to other jobs. Instead, the commands in a resource list perform variable evaluation dictating the behavior of the job. Depending on the results of the variable evaluation, the job run can be suppressed, put in a wait state, or a new value can be assigned to a variable.

In addition to the resource list, the initiate list, the prerequisite list and the end actions list can also be used for advanced job interaction, though in different ways. Each of these methods is explained later in this section.

3.1.1 How jobs are processed

In order to understand advanced job interaction, you should first understand how jobs are processed and what techniques can be used to add to that process. This list illustrates the order that job lists are processed and the type of advanced job processing that can be performed using these lists.

1. Job is initiated - A job can be initiated either by a start time, a submit command or another jobs initiate list)
2. Prerequisites - The first step of a job is the processing of the prerequisites list. The prerequisite job checks to see if the prerequisites have successfully executed. If all prerequisites have been executed, the next step occurs. The prerequisite list can include IF statements that include or exclude particular jobs.
3. Resources - The resource list is where the bulk of advanced job programming occurs. Here IF-THEN statements are processed that can check or alter the value of a variable, suppress a job run or cause a wait to occur. These techniques will prove very useful.
4. Job is run - The job is submitted into batch using the attributes assigned for the job.
5. End Action - The end action list contains post job processing that occurs whether or not the job is successful. The end action list can include IF-THEN statements that checks or alters the value of a variable.
6. Initiates - The initiates list contains the jobs that will be executed upon successful completion of the current job. The initiate list can include IF statements include or exclude particular jobs. Other conditions can also be used to control the next job step.

The following examples illustrate some situations where advanced job interaction can be used. While reading these descriptions, see if they apply to a job scheduling challenge you may have in your job set. You can most likely use the advanced job interaction tools to solve this challenge.

• Job switching - One advanced job technique is to switch between jobs by setting a variable that determines "if the variable is A then run these jobs, if the variable is B then run these other jobs". This type of job switching is useful for a jobs that need to be run in certain situations that may be unpredictable. However, variables can be used for a number of other purposes in addition to these.
• Reservation system - A reservation system is a powerful tool that let's you determine whether the job will run based on the value of an integer. For instance, suppose you have a limited amount of disk space and your jobs require the use of a certain amount of disk space. You can assign each job a variable in the form of an integer and then subtract that integer from a total available disk space integer. When the maximum disk space available is used up, job will be queues up using a simple IF-THEN construct.
• Job intersection - The intersection method is especially useful where you only want a single job to run at a time. Suppose you have a job set that updates a database using a number of jobs. However, the database can only be opened and updated by one job at a time. Using the job intersection method, the jobs can be set up to run exclusive of each other by setting a variable that prevents other jobs from running whenever a job executes. This can be done using variable assignments and IF-THEN constructs.
• Shut off valve - The shut off valve is a way to turn off all or some of the jobs in a job run by manually setting a variable to off. By inserting the line

  IF valve == off THEN SUPPRESS_RUN

  
  into each of the jobs in a run, you can manually turn off all the jobs for as long as you want by changing the variable to off. When you want to run the jobs again, simply change the variable to anything but off.

• Status variables - A status can be displayed using variables which change in the MOTIF display. Every time a variable is changed all monitor displays are notified and the display updated.

This section displays the syntax that can be used to perform advanced job interaction in Schedule. There are four list types that can be used in advanced job interaction. These are:

List type	Allowable constructs
Prerequisites list	Job names,IF expression
Resource list	!Comment SET variable=expression IF expression THEN WAIT IF expression THEN SUPPRESS_RUN IF expression THEN SET variable=expression IF FILE_NOT_FOUND THEN expression
End action list	!Comment SET variable=expression IF expression THEN SET variable=expression
Initiates list	Job name, IF expression

Make a decision as to whether a variable will be updated.

Usage: Resource list/end action list

If the expression evaluates to true then variable will be updated. Other wise the statement is ignored and the next statement is evaluated.

The operator FILE_NOT_FOUND can be used in any IF-THEN statement. It tests for the presence of one or more files and evaluates to true if the file is not present. The file name specification can include wildcards.

Format

IF expression THEN SET variable = expression

Examples

IF run_count == 5 THEN SET total=counter-5 
      

IF FILE_NOT_FOUND test1.dat THEN set test=0 
      

Make a decision as to whether the job run should be failed.

Usage: Resource list

If the expression evaluates to true then the job will fail and no other resource statements are evaluated. The resource list will not be evaluated again. If the expression evaluates to false than the statement is ignored and the next statement is evaluated.

The operator FILE_NOT_FOUND can be used in any IF-THEN statement. It tests for the presence of one or more files and evaluates to true if the file is not present. The file name specification can include wildcards.

Format

IF expression THEN FAILRUN

Examples

IF fail_var == "YES"  THEN FAILRUN 
      

IF FILE_NOT_FOUND test1.dat THEN FAILRUN 
      

Make a decision as to whether the job run should be suppressed.

Usage: Resource list

If the expression evaluates to true then the job is not executed and no other resource statements are evaluated. The resource list will not be evaluated again. If the expression evaluates to false than the statement is ignored and the next statement is evaluated.

The operator FILE_NOT_FOUND can be used in any IF-THEN statement. It tests for the presence of one or more files and evaluates to true if the file is not present. The file name specification can include wildcards.

Format

IF expression THEN SUPPRESS_RUN

Examples

IF total != 5 THEN SUPPRESS_RUN 
      

IF FILE_NOT_FOUND test1.dat THEN SUPPRESS_RUN 
      

Make a decision as to whether the job should go into a wait state.

Usage: Resource list

If the expression evaluates to true then the job waits and no other resource statements are evaluated. The entire resource list will be re-evaluated from the begininning at a later time. If the expression evaluates to false than the statement is ignored and the next statement is evaluated.

The operator FILE_NOT_FOUND can be used in any IF-THEN statement. It tests for the presence of one or more files and evaluates to true if the file is not present. The file name specification can include wildcards.

Format

IF expression THEN WAIT

Examples

IF complete >= 5 THEN WAIT 
      

IF FILE_NOT_FOUND test1.dat THEN WAIT 
      

Includes the resource/end actions of another job.

Usage: Resource list/end actions list

Format

INCLUDE job_name

Examples

 
 
 
 
include /jobs/typical_job 
include /jobs/test/example_job 
 
 
      

Set the value of a single variable.

Usage: Resource list/end actions list

Format

SET variable=expression

Examples

SET next_var = 5 
      

3.1.4 Operators

Table 3-1 Assignment operator

Operator	Description
A = B	Assigns the value of B to A

Table 3-2 Integer operators

Operator	Alternate	Description
A < B	A .LT. B	Evaluates to true if A is less than B
A > B	A .GT. B	Evaluates to true if A is greater than B
A <= B	A .LE. B	Evaluates to true if A is less than or equal to B
A >= B	A .GE. B	Evaluates to true if A is greater than or equal to
A == B	A .EQ. B	Evaluates to true if A is equal to B
A != B	A .NE. B	Evaluates to true if A is not equal to B
A + B		Evaluates to the sum of A and B
A - B		Evaluates to the difference between A and B
A * B		Evaluates to the product of A and B
A / B		Evaluates to the quotient of A and B
A % B		Evaluates to the integer remainder of B and A

Table 3-3 String operators

Operator	Description
A .LTS. B	Evaluates to true if A is less than B
A .GTS. B	Evaluates to true if A is greater than B
A .LES. B	Evaluates to true if A is less than or equal to B
A .GES. B	Evaluates to true if A is greater than or equal to B
A .NES. B	Evaluates to true if A is not equal to B
A .EQS. B	Evaluates to true if A is equal to B

Table 3-4 BOOLEAN operators

Operator	Description
A .AND. B	Evaluates to true if both A and B evaluate to true
A .OR. B	Evaluates to true if either A or B evaluate to true
.NOT. A	Evaluates to true if A evaluates to false
FILE_NOT_FOUND	Evaluates to true if filename is found