Software that is distributed to fix a problem in a product is called an update. Updates are installed with either the Web-based System Manager Software application or with SMIT. Updates are also installed with the installp command.
If you choose to apply the updates during installation (rather than committing them at installation time), you can still reject those updates later. If a particular update is causing problems on your system, you can reject that update without having to reject all the other updates that you installed. Once you are convinced that the updates cause no problems, you may want to commit those updates to retrieve the disk space that is used to save the previous levels of that software.
All software products have a version number and a release number that identify the release level of the product. In addition to this, product updates are assigned a modification level number and a fix level number to identify the level of the update.
Each AIX Version 4.3 formatted update package has a unique mod and fix level associated with it. The mod and fix level becomes a part of the product level for each software product fileset that is part of the update package. If the situation occurs where the fix for one problem spans across filesets, then a separate mod and fix ID is assigned to each fileset update package.
Following is an example of a fileset and a fileset update:
bos.net.tcp.client 4.1.0.0 is a fileset. bos.net.tcp.client 4.1.0.1 is an update to that fileset. If another fileset update, bos.net.tcp.client 4.1.0.2, is generated, this update will contain all the fixes that were in the bos.net.tcp.client 4.1.0.1. If a cumulative AIX update is generated, the mod level of the fileset will increment, resulting in bos.net.tcp.client 4.1.1.0, which would contain all previous fixes.