Install each Oracle product in its own Oracle home.

The value for %ORACLE_BASE% is stored in the registry (for example, in HKEY_LOCAL_MACHINE\SOFTWARE\ORACLE\HOME0). The values for ORACLE_HOME and ORACLE_SID are also stored in the registry. Symbolic links for these directories, like those used on UNIX platforms, are not supported on Windows platforms.

Oracle Universal Installer (OUI) records the values for environment variables such as ORACLE_BASE, ORACLE_HOME, and ORACLE_SID in the registry and also updates the value for the PATH environment variable for the user performing the installation. In Linux and UNIX systems, you must manually set these environment variables in the user session or user profile.

• Changing the Current Setting for Oracle Home
  Use Oracle Universal Installer (OUI) to change the current Oracle home.