source: Racker Hacker

rpm hangs after printing this error : “rpmdb: Lock table is out of available object entries”.

First, kill (-9) all hanged rpm processes. Then remove the corrupted databases, and rebuild them.

rm /var/lib/rpm/__db.*
rpm --rebuilddb

Tip: if this happens on a server, check that yum-updatesd is not running. yum-updatesd can be the source of such errors. yum-updatesd is evil. I don’t think that yum-updatesd is useful on a server anyway.
chkconfig yum-updatesd off
service yum-updatesd stop