In this paper, we have presented five self-healing database
system architectures which can be built on top of COTS
components. These architectures indicate that: (1) a
multi-layer, defense-in-depth approach, as summarized in
Figure 6, is usually more cost-effective than having the
system’s survivability depend on the effectiveness of one or
two mechanisms such as intrusion detection; (2) adaptive
intrusion-tolerant mechanisms are usually more
cost-effective than pre-programmed intrusion tolerant
mechanisms; (3) service-oriented, intrusion-tolerant
database systems are usually more cost-effective than
state-oriented, intrusion-tolerant database systems. Finally,
we would like to restate that OS-level and transaction-level
self-healing mechanisms should be seamlessly integrated to
build multi-layer, self-healing database systems. This
integration requires careful study of the relationships
between these two layers of mechanisms. For example,
although OS-level data corruptions cannot be detected
using transaction-level approaches, transaction-level
approaches can be very useful to recover from these
corruptions.