Database Reference
In-Depth Information
ora12cr1 19675 1 0 15:16 ? 00:00:00 ora_cjq0_ora12cr1
ora12cr1 19705 1 0 15:16 ? 00:00:00 ora_w000_ora12cr1
ora12cr1 19708 1 0 15:16 ? 00:00:00 ora_qm02_ora12cr1
ora12cr1 19712 1 0 15:16 ? 00:00:00 ora_q002_ora12cr1
ora12cr1 19714 1 0 15:16 ? 00:00:00 ora_q003_ora12cr1
tkyte 19732 19731 0 15:17 pts/0 00:00:00 /home/ora12cr1/app/ora12cr1/product/12.1.0/dbhome_1/
bin/sqlplus
ora12cr1 19733 19732 0 15:17 ? 00:00:00 oracleora12cr1 (DESCRIPTION=(LOCAL=YES)
(ADDRESS=(PROTOCOL=beq)))
tkyte 19744 19742 0 15:18 pts/0 00:00:00 grep ora12cr1
Now you can see that there is a new process,
oracleora12cr1
, created as our dedicated server process. When we
log out, the extra thread/process will go away.
This brings us to the next iteration of our diagram. If we were to connect to Oracle in its most commonly used
configuration, we would see something like Figure
2-2
.
Instance
Background
Process
Background
Process
Background
Process
Background
Process
Background
Process
Background
Process
SGA
Database
File
File
Client
Connection
Dedicated
Server
File
File
File
File
Figure 2-2.
Typical dedicated server configuration
As noted, typically Oracle will create a new process for me when I log in. This is commonly referred to as the
dedicated server configuration, since a server process will be dedicated to me for the life of my session. For each
session, a new dedicated server will appear in a one-to-one mapping. This dedicated server process is not (by
definition) part of the instance. My client process (whatever program is trying to connect to the database) will be in
direct communication with this dedicated server over some networking conduit, such as a TCP/IP socket. It is this
server process that will receive my SQL and execute it for me. It will read data files if necessary, and it will look in the
database's cache for my data. It will perform my update statements. It will run my PL/SQL code. Its only goal is to
respond to the SQL calls I submit to it.
Shared Server
Oracle can also accept connections in a manner called
shared server
, in which you wouldn't see an additional thread
created or a new UNIX/Linux process appear for each user connection.
