z/OS system installation and maintenance
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z/OS system customization

z/OS system installation and maintenance

System customization (also known as tailoring) is the overall process by which an installation selects its operating system. System programmers thoroughly plan and complete the steps in this process, selecting system options through several different mechanisms.

System customization is accomplished through the following mechanisms:
MVS™ hardware configuration definition (HCD)
System programmers use the HCD dialog to perform a variety of tasks, including defining the operating system and hardware configurations, activating configuration data (that is, applying configuration changes to the system), and querying or printing configuration data.
Initialization-time selections
When initializing the operating system, system programmers tailor the system environment through several sources, including operator actions, customization data in system libraries (SYS1.PARMLIB and other parmlib data sets), and job control language (JCL) for the master scheduler subsystem.
Implicit system parameters
Various system requirements affect the way the system performs. These system requirements may be considered as "implicit" parameters. They involve DD statements, data sets, hardware choices, and so forth. Some examples are:
  • SYSABEND, SYSMDUMP, and SYSUDUMP DD statements.
  • The System Management Facilities (SMF) data sets.
  • Addition of new modules to the LPALST concatenation.
  • Choice of the device on which the PLPA paging data sets will reside.
  • Definition of page data sets through the DEFINE PAGESPACE command.
  • z/OS system libraries
    The z/OS® system libraries contain customization data that is essential to the running of the z/OS system. Some of these data sets are related to IPL processing, while others are related to the search order of invoked programs or to system security, among other functions.
  • System symbols in PARMLIB
    System symbols are elements that allow different z/OS systems to share PARMLIB definitions while retaining unique values in those definitions. System symbols act like variables in a program; they can take on different values, based on the input to the program.
  • Search order for programs
    Modules (programs), whether stored as load modules or program objects, must be loaded into both virtual storage and central storage before they can be run. When one module calls another module, either directly by asking for it to be run or indirectly by requesting a system service that uses it, it does not begin to run instantly. How long it takes before a requested module begins to run depends on where in its search order the system finds a usable copy and on how long it takes the system to make the copy it finds available.
  • Input/output (I/O) device configuration
    The I/O configurations to the operating system (software) and the channel subsystem (hardware) must be defined. The Hardware Configuration Definition (HCD) component of z/OS consolidates the hardware and software I/O configuration processes under a single interactive end-user interface.
  • Console configuration
    Operating z/OS involves managing hardware such as processors and peripheral devices (including the consoles where your operators do their work); and software such as the z/OS operating control system, the job entry subsystem, subsystems (such as NetView®) that can control automated operations, and all the applications that run on z/OS.

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