PTFs used to be distributed in a group on a so-called
Program Update Tape (
PUT) or
Recommended Service Upgrade (
RSU), approximately on a monthly basis. They can now be downloaded straight to the system through a direct connection to IBM support. In some instances IBM will release a "Cumulative PTF Pack", a large number of fixes which function best as a whole, and are sometimes codependent. When this happens, IBM issues compact discs containing the entire PTF pack, which can be loaded directly onto the system from its media drive. One reason for the use of physical media is size, and related (default) size limits. "By default, the /home
file system on VIOS (Virtual I/O Server) for
System p is only 10GB in size."{{cite web |title=Populating the VIOS Virtual Media Repository In
z/OS, the PTFs are processed using
SMP/E (System Modification Program/Extended) in several stages over a course of weeks. Each PTF may include
HOLDDATA, in which case it is known as an
exception SYSMOD. In rare cases an installation may install a single PTF, but normally it will install all available service except PTFs excluded by, e.g., aging policies, HOLDDATA. Details vary from installation to installation, but a simple service cycle would involve these steps: • Download the most recent HOLDDATA •
RECEIVE (load) the service and HOLDDATA to the
Consolidated Software Inventory (
CSI) •
APPLY CHECK the service and HOLDDATA to list exception SYSMODs, verify that necessary prerequisites are available, and to list potential problems, e.g., errors. • Review exception SYSMODs for, e.g., ACTION, DOC, holds. • Update documentation to reflect the exception SYSMODs, and take any necessary actions • Order and RECEIVE any missing prerequisites. •
RESTORE,
REJECT, rework and re-APPLY any local exits or modifications affected by the service. •
APPLY the service to one system in a
cluster (if available), and review the system's performance over multiple weeks to ensure it does not hinder your productivity or functionality • Selectively
BYPASS HOLDDATA when appropriate •
RECEIVE and APPLY the service to the production system and monitor its effects for several weeks If the system is adversely affected by the service, a
system administrator may sometimes selectively
RESTORE (un-apply) it and seek further support from IBM. However, if no problems are found after the service is applied, it can be permanently installed,
ACCEPTed (committed) to the system. These repairs to IBM software are often in response to APARs submitted by customers and others and acted on by IBM, and are a common first step to resolving software errors. It is generally expected by the customer that the problem would be fully corrected in the next release (version) of the relevant product. == Terminology and variants ==