I had a support specialist today that had an open yum task they couldn’t kill gracefully, after kill -9, this was happening
[root@mybox home]# yum list | grep -i xml rpmdb: Thread/process 31902/140347322918656 failed: Thread died in Berkeley DB library error: db3 error(-30974) from dbenv->failchk: DB_RUNRECOVERY: Fatal error, run database recovery error: cannot open Packages index using db3 - (-30974) error: cannot open Packages database in /var/lib/rpm CRITICAL:yum.main: Error: rpmdb open failed [root@mybox home]#
The solution to fix this is to manually erase the yumdb and to manually rebuild it;
[root@mybox home]# rm -f /var/lib/rpm/__* [root@mybox home]# rpm --rebuilddb