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SAF (System Authorization Facility)

  • This is the z/OS component that manages security on the system. All security requests go to SAF. SAF can be used alone, or it can more securely be used with a security manager like RACF, ACF2, or Top Secret.

Think of Task Manager on Windows.

  • A program that runs on MVS that shows jobs running and job output.

SE (Support Element)

this is the laptop connected to door on the mainframe box.

  • This is the management console mounted directly to the z/OS box.

Second Level System

  • An operating system that is running on z/VM or some hypervisor.

Security Context

  • The security metadata associated with the user that is attached to their address space and all of their threads and procosess.

Sequential Data Set

  • This is a flat file on z/OS. In other words the data set represents only one file. For example, only one distinct program or entity can be written to a sequential data set.

SLA (Service Level Agreement)

This is just something that a business guarantees to the user.

  • Obligations that banks and enterprises have for their customers. (i.e. All credit card transactions are guaranteed to take 8 ms)


  • This is a 4 kilobytes page of auxiliary storage/memory, meaning that this is storage/memory that has been swapped out to disk due to inactivity.

SIE (Set Interpretive Execution)

  • This is a special assembly instruction used to give control to a virtual machine guest. In general, this instructuon enables secure machine virtualization on s390x architecture.

Single CSECT Module

  • This is a load module that is composed of only one segment or control section.

SMP/E (System Modification Program Extended)

This is analogus to the the package managers used on Linux like apt-get, apk, and yum.

  • SMP/E is used to manage the installation of z/OS software products and fixes.

SMP/E Installable Package

  • This is a package of distribution libraries shipped to customers. This package contains the SMPMCS files and relfiles.

SMPCSI (SMP Consolidated Service Inventory)

  • This is a VSAM data set used by SMP/E for controlling z/OS product installation and recording the results.

SMPMCS (SMP Modification Control Statements)

  • This is a metadata file used by SMP/E to tell it how to install a product or update on the system.

SMPMTS (SMP Macro Temporary Storage)

  • Used by SMP/E as temporary storage for Macros during installation time.


  • Data set used by SMP/E to manitain base versions of load modules.


  • Data set used by SMP/E as a temporary repository where SYSMODS are recieved and stored until they are installed.


  • Data set used to backup libraries installed on the system.

SMPSTS (SMP Source Temporary Storage)

  • Data set used by SMP/E as temporary storage for source during installation time.

SMS (System Managed Storage)

  • This is a component used to automate the management of DASD and storage on z/OS.

SMT (Simultaneous Multithreading)

This is similar to the hyperthreading capabilities that are supported on many Intel processors.

  • Simultaneous multithreading allows two threads to be handled on one processor core. This feature is supported on IFL and zIIP processors.

SNA (Systems Network Architecture)

Think TCP/IP.

  • This is a networking protocol. A key difference between SNA and TCP/IP is that a session must first be established before two servers can communicate.

SRB (Service Request Block)

  • This is a block of memory that represents a request to the system for a system service.


  • This is not disk. This is actually memory/RAM.


  • In SMP/E, SUP is specified as part of the ++VER SMPMCS statement to define an FMID/product that the FMID/product being installed supercedes/replaces.


  • The Kernel of z/OS.

Supervisor State

  • A program that is running with operating system level privileges.

SVC (Supervisor Call)

Like syscall on Linux.

  • This is a call/interrupt to have the system do something on the user program’s behalf.

SVCLIB (Supervisor Call Library)

  • Library/directory that contains supervisor calls.


  • In SMP/E, this is used to refer to target libraries where an element will be installed.

SYSLOG (System Log)

  • This is the accumulation of messages generated by operators, programs, and system components.

SYSMOD (System Modification)

  • This is an SMP/E term used to refer to anything that modifies the system.

SYSPROG (System Programmer)

  • The person who manages the system. The system programmer’s job is to install software updates and patches, configure the system, and request hardware resources.


  • This is the input data set/file for a JCL job step.


  • This is the output data set/file for a JCL job step.


  • This is where all of the system data sets are stored (MACLIB, LPALIB, LINKLIB, etc…).


  • This is a mechanism for linking disparate z/OS systems together using a coupling facility.

Sysplex Timer:

  • This is a mechanism for synchronizing the clock of all members of a sysplex.

SYSRES (System Residence Volume)

Think of the hard drive or SSD that your PC boots from.

  • This is the disk device where the operating system is loaded from.

System Variable

System Variables can be thought of as analogous to environment variables on Linux.

  • These are system defined global variables that can be used within JCL.