System Installation Choices › SMP/E Analysis › Installation and Maintenance

Installation and Maintenance

When z/OS was first developed, you installed or changed the operating system and its components using the system generation (SYSGEN) process. z/OS options and parameters were described in macros that were then assembled and link‑edited. This process was lengthy and involved multiple steps that could introduce errors.

The SYSGEN process has been replaced by easier-to-use pregenerated methods of packaging which greatly simplify the installation process. One such implementation is a partially generated z/OS system called installation productivity option (IPO). Although IPO was the custom built installation process offering (CBIPO) or custom built product delivery offering (CBPDO), the concept remains the same. With CBIPO or CBPDO, IBM copies the components and products that you order on to a tape and ships it to you. This tape contains load modules, object modules, macro libraries, and distribution libraries. Many of these libraries come ready to use, so they just have to be copied on to your system.

If you are installing z/OS for the first time or completely replacing your existing system, you should consider installing a CBIPO. The CBIPO system contains program temporary fixes (PTFs) for a specific maintenance level (genlevel) of the operating system. These PTFs are generally available on program update tapes (PUT tapes). PUT tapes contain maintenance that IBM distributes about every six weeks. CBIPO is recommended for large‑scale changes and requires less skill to install than a CBPDO. However, if you want to upgrade your existing system or update a specific component or subsystem, you should consider using a CBPDO. The CBPDO system includes PTFs that are not yet released on PUT tapes. The CBPDO is meant for incremental changes and requires more skill to install than a CBIPO.

Both CBIPO and CBPDO considerably simplify the installation process.

Even with CBIPO and CBPDO, you can find the installation and maintenance process confusing, time‑consuming, and error‑prone. This is because you must still separately install other vendor products, outstanding fixes, local user modifications (USERMODs), and exits to generate a new z/OS system.

To maintain an existing system, you must continually install PUT tapes containing outstanding fixes. Occasionally, during the maintenance process, these fixes inadvertently overlay other fixes that are necessary. This can impact other parts of the system. IBM avoided these maintenance problems by requiring that fixes be applied only when other fixes were already installed. Soon, however, the coordination of all of these fixes and their requirements became too complex to handle manually, so IBM developed SMP/E to mechanize the installation and maintenance of z/OS system software.