For example,
state information contains information about the SQL statements executed by the
session. When youu se a dedicated server, this state is stored in the private memory
used by the dedicated server. This works out well because the dedicated server works
with only one client. The term for this private memory is the Program Global Area
(PGA).
If you??™re using the shared servers, however, any server can work on behalf of a specific
client. The session state cannot be stored in the PGA of the shared server
process. All servers must be able to access the session state because the session can
migrate between different shared servers. For this reason, Oracle places this state
information in the System Global Area (SGA).
All servers can read from the SGA. Putting the state information in the SGA allows a
session and its state to move from one shared server to another for processing different
requests. The server that picks up the request from the request queue simply
reads the session state from the SGA, updates the state as needed for processing, and
puts it back in the SGA when processing has finished.
Pages:
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185