(g)urpmi will install priority upgrades first then restart itself.
If the priority upgrades happen to be installed in more than one transaction
code in the rpm packages %post script to clear out the rpmdb index files
could be run after the first transaction and then the second transaction
could regenerate these indexes using the current libdb version in memory.
This results in the rpmdb not being readable and requires manual intervension.
If the initial priority upgrades are handled in a single transaction this does
not occur and the rpmdb indexes are regenerated with the correct libdb.
This is a workaround to ensure that the first (g)urpmi run is completed in
a single transaction but it shoud only update enough to ensure urpmi and rpm
are upgraded. The normal --auto-select cycle can continue thereafter.
Ideally this would actually be fixed in urpmi to ensure that any priority updates
are handled within a single transaction.