By default, Release Patch Kits are made reversible during the installation so you revert your system to its state prior to the installation. If you choose to make patch kits nonreversible, you will not be able to uninstall the kit.
Customer-Specific patch kits are forced to be reversible when the CSP kit is manufactured. This forced reversibility overrides the reversibility option provided by dupatch during installation.
Patch reversibility is dependent upon saving the existing system files that will be updated by the patch. Saving these files requires the availability of adequate storage space in /var/adm/patch/backup, which can be a mount point for a separate disk partition, an NFS mount point, or a symbolic link to another file system. This allows you to configure your system to reduce the impact on system disk space for the /, /usr, and /var partitions.
The dupatch utility checks for the required storage space prior to patch installation. Patch installation is prevented if adequate backup space is unavailable.
“Performing a Patch Preinstallation Check” includes an example of the dupatch output regarding patch reversibility.