The client
must now be able to depend on a server process that is always available to complete
the connection. Because a shared server process may be servicing another
client, the client connects to a dispatcher, which is always ready to receive any
client request. There are separate dispatchers for each network protocol being
used (e.g., dispatchers for TCP/IP, etc.). The dispatchers serve as surrogate dedicated
servers for the clients. Clients directly connect to their dispatchers instead
of to a server. The dispatchers accept requests from clients and place them in a
request queue, which is a memory structure in the SGA. There is one request
queue for each instance.
Shared servers
The shared server processes read from the request queue, process the requests,
and place the results in the response queue for the appropriate dispatcher. There
is one response queue for each dispatcher. The dispatcher then reads the results
from the response queue and sends the information back to the client process.
There is a pool of dispatchers and a pool of shared servers.
Pages:
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182