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z/OS Jewel Keeper: SYS1.PARMLIB

June 22, 2014

In my previous post, I wrote that the Message Processing Facility (MPF) of z/OS is at the intersection of usability and automation. It is an important component of z/OS that you might now know about unless you have some system programming in your background. I mentioned that MPF uses a member of SYS1.PARMLIB named MPFLSTxx. If you are new to the dataset SYS1.PARMLIB, you might be wondering what is it and what other definition members of z/OS are kept there.

SYS1.PARMLIB is a required partitioned data set that contains IBM-supplied members and others created by the company running z/OS. The dataset contains lists of system parameter values that are used by almost every component of z/OS. This is the most important data set in a z/OS operating system.

SYS1.PARMLIB is read by the system at IPL and later by components like the System Resource Manager and UNIX System Services. It can also contain commands automatically issued at system initialization. This is very useful to do things like start automation to handle the start up of subsystems used in z/OS systems. Basically, SYS1.PARMLIB contains many initialization parameters in a pre-defined form, contained in a single data set, minimizing the need for the operator to enter parameters.  

A Few Examples

Here is a description of three sample members that relate to automating z/OS systems:

  • COMMNDxx—It containscommands to be issued by the control program immediately after initialization. This is the technique that is use to start the system automation subsystem that automatically handles the complexity and dependencies associated with bringing up the many started tasks and jobs that run in a z/OS system.
  • IEFSSNxx—It contains parameters that identify what subsystems are to be initialized. When automation of the system is used, the program that handles the system automation is usually identifies as a subsystem.
  • MPFLSTxx—It containsparameters that the MPF uses to control message handling and display. I wrote about MPF in a previous post.

I have focused on SYS1.PARAMLIB and definitions that relate to automation because that is the subject of next week’s post.

Where can I read more about SYS1.PARMLIB?  All parameters of the SYS1.PARMLIB data set are described in z/OS MVS Initialization and Tuning Reference, SA22-7592.  


Posted June 22, 2014 | Permalink

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