Error:

[root@localhost ~]# yum clean all
error: db5 error(11) from dbenv->open: Resource temporarily unavailable
error: cannot open Packages index using db5 – Resource temporarily unavailable (11)
error: cannot open Packages database in /var/lib/rpm
CRITICAL:yum.main:

Error: rpmdb open failed

Fix:
cp -a /var/lib/rpm/ /var/lib/rpm___
rm -rf /var/lib/rpm/__db*
rpm –rebuilddb
yum update