Databases Reference
In-Depth Information
Figure 10: A persistent distributed shared virtual memory
Caching and clustering
WAKASHI is for distributed and parallel processing of a database. The database
files should be distributed over distributed sites in order to increase the total system
performance. The storage manager of ShusseUo, WAKASHI controls the concurrent
accesses to database files and manages the distributed cache of heap. Once a data
page of a heap is transferred, the page data is cached until the page data becomes
invalid by as the result of a page write.
INADA is a class library that provides an ODMG 2.0 C++ binding OML and
ODMG C++ objects and provides services by which a client program manages
persistent objects. The interface for object creation is an object constructor with a
new
operator, and the
delete
operator is provided for object deletion. INADA
receives a request to create or destroy an object and allocates or releases a memory
block in a persistent heap.
Persistent heaps can be distributed, and so persistent objects can be distributed.
The two types of object distribution are as follows.
•
dynamic distribution:
Persistent objects are stored in heaps in one site. WAKASHI allows
programmers to write location transparent client programs. The same client
program can run on a different site because copies of the data pages that
contain object data are transferred and cached automatically by the
WAKASHI mechanism at program execution.
•
static distribution:
Persistent objects are stored into distributed heaps. Objects are distributed
at their creation. The network cost can be reduced if the distribution of
objects and the execution site of the program are carefully designed.
