If you have trouble connecting to the YUM repository and everything seem ok.
yum list available
http://public.dhe.ibm.com/software/ibmi/products/pase/rpms/repo/repodata/repomd.xml: [Errno 12] Timeout on http://public.dhe.ibm.com/software/ibmi/products/pase/rpms/repo/repodata/repomd.xml: (28, 'Operation too slow. Less than 1000 bytes/sec transferred the last 30 seconds')
Trying other mirror.Maybe /QOpenSys/etc/yum/yum.conf file is corrupted and you can restore it from backup or copy from another LPAR.