Which procedure you should use depends on which OS is installed, which SRU, if any, is installed, and which package repository the system is configured to use.
If your system is running 11.1 or 11.1 with an SRU, follow the instructions in How to Update a System Running 11.1 to Oracle Solaris 11.2.
If your system is running 11 11/11 and an SRU, follow the instructions in How to Update a System Running 11 11/11 with an SRU to Oracle Solaris 11.2
If your system is running 11 11/11 and is using the release repository, follow the instructions in How to Update a System Running 11 11/11 to Oracle Solaris 11.2 Using the Release Repository.