Database validation allows to run low-level checks of consistency of on-disk
structures and even to fix some minor corruptions. It is recommended procedure
for any valuable database, i.e. DBA should validate database from time to time
to make sure it is healthy. But validation process requires exclusive access to
database, i.e. it forbids any kind of concurrent access to database while
validation run. It could be a big problem to stop user access, especially when
database is large and validation takes notable amount of time.
Online validation is a new feature which allows to perform some consistency
checks without exclusive access to database.
More details will follow in doc/README.online_validation