In a
non-interactive computer system, particularly
IBM mainframes, a job stream, jobstream, or simply
job
Work or labor (or labour in British English) is intentional activity people perform to support the needs and wants of themselves, others, or a wider community. In the context of economics, work can be viewed as the human activity that contr ...
is the sequence of
job control language
Job Control Language (JCL) is a name for scripting languages used on IBM mainframe operating systems to instruct the system on how to run a batch job or start a subsystem.
More specifically, the purpose of JCL is to say which programs to run, ...
statements (JCL) and data (called ''instream data'') that comprise a single "unit of work for an operating system".
The term ''job'' traditionally means a one-off piece of work, and is contrasted with a ''batch'' (executing the same steps over many inputs), but non-interactive computation has come to be called "
batch processing
Computerized batch processing is a method of running software programs called jobs in batches automatically. While users are required to submit the jobs, no other interaction by the user is required to process the batch. Batches may automatically ...
", and thus a unit of batch processing is often called a ''job'', or by the oxymoronic term
batch job
Computerized batch processing is a method of running software programs called jobs in batches automatically. While users are required to submit the jobs, no other interaction by the user is required to process the batch. Batches may automatically ...
; see ''
job
Work or labor (or labour in British English) is intentional activity people perform to support the needs and wants of themselves, others, or a wider community. In the context of economics, work can be viewed as the human activity that contr ...
'' for details. Performing a job consists of
executing one or more
programs. Each program execution, called a ''job step'', ''jobstep'', or ''step'', is usually related in some way to the others in the job. Steps in a job are executed sequentially, possibly depending on the results of previous steps, particularly in batch processing.
The term "job stream" is particularly associated with mainframes; in the
IBM z/OS
z/OS is a 64-bit operating system for IBM z/Architecture mainframes, introduced by IBM in October 2000. It derives from and is the successor to OS/390, which in turn was preceded by a string of MVS versions.Starting with the earliest:
* ...
operating system, a job is initiated by a
// JOB and terminated by the next
// JOB or
// statement. Each job step consists of one
// EXEC statement indicating the program to be executed and usually multiple
// DD statements defining the
files and devices to be used.
Example
A simple example of a job stream is a system to print payroll checks which might consist of the following steps, performed on a batch of inputs:
# Read a file of data containing employee id numbers and hours worked for the current pay period (batch of input data). Validate the data to check that the employee numbers are valid and that the hours worked are reasonable.
# Compute salary and deductions for the current pay period based on hours input and pay rate and deductions from the employee's master record. Update the employee master "year-to-date" figures and create a file of records containing information to be used in the following steps.
# Print payroll checks using the data created in the previous step.
# Update bank account balance to reflect check numbers and amounts written.
Each step depends on successful completion of the previous step. For example, if incorrect data is input to the first step the job might terminate without executing the subsequent steps to allow the payroll department to correct the data and rerun the edit. If there are no errors the job will run to completion with no manual intervention.
See also
*
Job queue
In system software, a job queue ( batch queue, input queue), is a data structure maintained by job scheduler software containing jobs to run.
Users submit their programs that they want executed, "jobs", to the queue for batch processing.
The s ...
*
Job scheduler
A job scheduler is a computer application for controlling unattended background program execution of job (computing), jobs. This is commonly called batch scheduling, as execution of non-interactive jobs is often called batch processing, though tr ...
References
IBM mainframe operating systems
Job scheduling
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