It is highly recommended that you uninstall any previous versions of XL Fortran before you install XL Fortran V10.1. If you use the xlf_install utility to install the new version to the default location (/opt/ibmcmp/), it will remove the old files for you.
However, advanced users might want to keep different versions of XL Fortran in /opt/ibmcmp/.
For example, you might want to meet all of the following criteria: