1 research outputs found
The construction of recoverable multi-level systems
PhD ThesisSystems structures and data structures which make
possible the state restoration of user objects, are
described in this thesis. Recovery is linked with types,
which suggests making a distinction between recoverable and
unrecoverable types. For convenience, recovery is discussed
in terms of recovery blocks as developed at the University
of Newcastle upon Tyne. Recovery is taken to mean restoring
the values of recoverable types.
Recoverable multi-level systems are considered. On the
one hand levels in such systems can be backed out. On the
other hand these levels provide explicit recovery for new
types they introduce, and so can be called on to restore
states of objects used in higher levels. The concepts and
issues are discussed and explained; mechanisms and
techniques for building such systems are presented.
Recovery techniques for complex global data structures
and techniques to maintain consistency at any time, even
when recovery is impossible such as after a crash, are
described and compared.
Many of the presented techniques are employed in an
implemented recoverable two-level system, with a recoverable
filing system. This two-level system is described in detail.
It is argued that in order to implement recoverability
in multi-level systems with efficiency and flexibility, the
interfaces of the system should provide both recoverable and
unrecoverable types.
It is also shown that the way in which complex data
structures are updated is of major importance if recovery is
to be provided in a "reasonably" efficient way and
consistency is to be guaranteed after a crash.Netherlands Organisation
for the Advancement of Pure Research