You can't use YUM to update your system.  You get something similar to this:

CRITICAL:yum.verbose.cli.yumcompletets:Yum Error: Error: rpmdb open failed
PLESK: The Yum utility failed to install the required packages.

Solution:

Remove the databases and then rebuild them.

Login via SSH
su -
<password>
cd /var/lib/rpm
rm __db*

yum clean all
rpm --rebuilddb
yum makecache
yum update

If you get this:

Warning: RPMDB altered outside of yum. Plesk

Try this:

yum history sync

Other things to try:

yum-complete-transaction

You could try running:

package-cleanup --problems
package-cleanup --dupes
rpm -Va --nofiles --nodigest