Single PTFs (fixes) are applied to correct specific
reported problems.
A single fix is tested by IBM and is made available to all IBM® customers.
Single fixes are capable of being downloaded with electronic customer support
or from the Internet and might also be available on media. Single fixes can
identify other single fixes as prerequisite, corequisite, or distribution
requisite fixes.
- HIPER PTFs
- A HIPER (High Impact PERvasive) PTF resolves
a problem that might have a high impact on IBM i5/OS™ operations
or a pervasive problem that affects most iSeries™ servers.
HIPER PTFs correct severe problems that occur on your system. HIPER PTFs represent two types of problems: high impact or pervasive and high impact and pervasive. Examples of these situations include the following:
- Your system might crash or hang and require a restart or IPL (initial program load) to recover.
- Your system might be stuck in a looping condition.
- Your system's data integrity might be threatened.
- Your system may experience a severe performance degradation, or the problem involves usability of a product's major function.
If any of the fixes are needed to address these situations
for your system, order and install the HIPER fixes. To help you manage HIPER
fixes, IBM maintains a HIPER PTF group that contains a list of all current
HIPER fixes for each supported i5/OS release.
For a complete listing of HIPER fixes, see the preventive service planning
information at the IBM eServer iSeries Support 
Web
site. - Prerequisite fix
A prerequisite fix is a fix that must be installed on your server before or at the same time as the fix that you want to install.
The system will prevent you from installing your fixes if you do not have the prerequisite fixes. Your fix cover letter or PSP information can identify other fixes that must be installed before or at the same time as the fix that you want to install.
- Corequisite fix
A corequisite fix must be installed at the same time as the fix that you are requesting to install.
Your fix cover letter or PSP information can identify other fixes that must be installed before or at the same time as the fix that you want to install. In addition, system error messages can notify you that the fix that you are attempting to install has requisite fixes. The system checks that the corequisite fixes are installed at the same time. In this case, you need to verify that your fixes installed successfully.
- Distribution requisite fix
A distribution requisite fix is required only for distribution purposes. The system does not require you to apply distribution requisite fixes, but it is recommended that they be applied with the dependent PTF. If you are sending a fix using Management Central, distribution requisite fixes are not sent.
- Delayed and immediate fixes
Some PTFs (fixes) can be applied without requiring an IPL and other fixes can be applied only during an IPL. The cover letter tells you if the PTF is immediate or delayed.
- Delayed fixes
- Delayed fixes can be applied only during an IPL. Delayed fixes
that affect the Licensed Internal Code can be applied immediately when the
server is running on the A storage area.
- Immediate fixes
- Immediate fixes can be applied without requiring an IPL if the objects that they affect are not in use. Immediate fixes can also be applied when you do the next IPL.