On some Red Hat distributions (CentOS, Fedora, Red Hat), the /usr/lib/rpm/rpmdb_verify command line tool can be used to determine there are any issues with the RPM database Packages file.

~]$ /usr/lib/rpm/rpmdb_verify /var/lib/rpm/Packages
BDB5105 Verification of /var/lib/rpm/Packages succeeded.

If the rpmdb_verify command detects an issue, you can rename the /var/lib/rpm/Packages file.

mv /var/lib/rpm/Packages /var/lib/rpm/Packages.old

And then use the rpmdb_dump and rpmdb_load commands to create a new RPM database Packages file.

/usr/lib/rpm/rpmdb_dump /var/lib/rpm/Packages.old | /usr/lib/rpm/rpmdb_load /var/lib/rpm/Packages

And then use the rpm command with the -vv and --rebuilddb flags to rebuild the RPM database.

rpm -vv --rebuilddb