On Mainframes, when you want to perform any task, you write a Job, and give it to the Mainframe Computer for processing. This is called submitting a job.
However, contrary to what you might fancy, your job doesn’t run immediately. Picture this - there are hundreds and thousands of Jobs, that are submitted on a Mainframe, minute-by-minute, every second, by different folks. How would the Mainframe computer decide which job goes first, and then which goes next and so on..
The MVS Operating System prepares a pretty time-table, a schedule, that goes something like this - JOB 1 runs at 12 o’ clock, JOB 2 runs at 1 o’ clock, JOB 3 runs at 2 o’ clock and so on.. Thus every job is allotted a time-slot(period) in the Mainframe's Calendar/time-table.
Before you are just about to submit a job on Mainframes, give your JCL a cursory-glance, to ensure it is syntactically-correct. Forgetting to put a comma, or inserting unnecessary extra-whitespaces, can lead to JCL-Errors. Be cautious about the Datasets begin used by the Job. For example, make sure you've already created the Input-Dataset AGY0157.DEMO.INPUT. Click here to get the contents of the Input-Dataset AGY0157.DEMO.INPUT, if you would like to execute the below-job. To submit a JOB on Mainframes, you must type SUBMIT command or just SUB, on the command line of the editor. I have shown below, how you submit a job on Mainframes.
![Image124[1]](http://lh5.ggpht.com/_sQvdFWqMlMg/S3RdquFSzWI/AAAAAAAACaM/CABQcyii3pg/Image124%5B1%5D_thumb%5B4%5D.png?imgmax=800 "Image124[1]")
When you press <Enter>, the Job AGY015A gets submitted to the Mainframe computer for processing. This is indicated by a *** message displayed at the bottom of the screen. The *** indicates, that TSO is waiting for me to read the message. As soon as you press <Enter> key again, the message goes away.
![Image125[1]](http://lh3.ggpht.com/_sQvdFWqMlMg/S3RdxeJl9jI/AAAAAAAACaU/r089ZQyLLN4/Image125%5B1%5D_thumb%5B3%5D.png?imgmax=800 "Image125[1]")
A common practice adopted by most Mainframe Programmers, is to code the NOTIFY parameter on the JOB Statement. Coding this parameter is quite useful, as it gives you an alert, a notification message, saying "The job AGY0157A has completed". ![Image126[1]](http://lh6.ggpht.com/_sQvdFWqMlMg/S3RdzdrQIyI/AAAAAAAACac/XBO2L25_2vI/Image126%5B1%5D_thumb%5B3%5D.png?imgmax=800 "Image126[1]")
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