PTF stands for Program Temporary Fix. When IBM becomes aware of a bug in its software (either a bug discovered by IBM or reported to IBM by someone like you), IBM first creates an Authorized Program Analysis Report (APAR) to study the problem and, if warranted, it creates a PTF that eradicates the bug. The reason it's called "temporary" is because IBM takes note of the problem and makes sure that the next release or modification of the software does not have the same bug.
You could be the first person to discover the bug, and it could be you who opens the APAR that ultimately generates the PTF. You can report a problem either by calling IBM Software Service or through ECS, described in Chapter 33.
If you have a problem with your system that looks like a genuinebug, you should report it to IBM immediately. Don't assume that someone else has reported it before you and that IBM already has a PTF to correct it.
As time passes, PTFs increase in numbers. For example, if a new release of the operating system is made available on January 1, there may be only 10 PTFs by February 1, but by March 1, there may be 20 more.
Each PTF corrects one problem and one problem only. They are called individual PTFs. IBM also puts together cumulative ("cume") PTFs, which are packages that contain most of the individual PTFs that have been issued since the beginning of the current release of the software. As time passes, IBM adds more individual PTFs, which necessitates a new cumulative PTF.
By far, the easiest way to manage PTFs is through the cume PTF packages. However, not all PTFs are made available through cume PTF packages. Although it should not happen, it does, and you need to keep up with the current PTFs as they are released.