The /var/lib/yum/plugins/local folder seems to store installed rpm packages:
$ ls /var/lib/yum/plugins/local
389-ds-base-1.2.11.15-95.el6_9.x86_64.rpm
389-ds-base-devel-1.2.11.15-95.el6_9.i686.rpm
...
yum-plugin-versionlock-1.1.30-42.el6_10.noarch.rpm
yum-updateonboot-1.1.30-42.el6_10.noarch.rpm
yum-utils-1.1.30-42.el6_10.noarch.rpm
At the same time, the directory has a pretty huge size: 2.9Gb.
The question is if it is safe to remove some RPM from there?