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Dedicated server process (Dedicated server)

For dedicated server configurations, when logging in, Oracle always creates a new process that specializes in this connection service for the lifetime of the session. For each session, a new dedicated server appears, and there is an one-to-one mapping between the session and the dedicated server. By definition, this dedicated server is not part of the instance. The user process and the server process are separate. Each user process has its own server process.

User processes and server processes can run on different machines to take advantage of distributed processing.

The ratio of user processes to server processes is 1 to 1.

Even if the user process does not make a database request, a dedicated server exists, but remains idle.

When to use a dedicated server

Submit batch jobs (expected to have little or no free time)

Connect as sysdba to start, shut down, or perform a restore

To request a dedicated server, it must be in the Oracle Net TNS connection string in the tnsnames.ora file

Contains the SERVER=DEDICATED clause.

Note: for most platforms, if your machine has enough memory to support dedicated servers, you should use dedicated servers

Server. The performance may be better this way.

There are exceptions, such as Windows NT, where, due to the asynchronous nature of the shared server architecture,

Performance may be improved with Oracle Shared Server configuration.

How to connect to a dedicated server

Set it in the tnsnames.ora file in the client server:

Dedicated = (DESCRIPTION =

(ADDRESS_LIST =

(ADDRESS = (PROTOCOL = TCP) (HOST = 192.168.1.52) (PORT = 1521))

)

(CONNECT_DATA =

(SERVICE_NAME = itpux)

(server = dedicated)

)

)

Shared server (shared server), officially called multithreaded server (Multi-Threaded Server) or MTS. In this way, no additional threads or new UNIX processes will be created for each user connection

Advantages of Oracle Shared Server

Reduce the number of processes for a routine

Increase the number of serviceable users

Achieve load balancin

Reduce the number of idle server processes

Reduce memory footprint and system overhead

How to connect to a shared server

You cannot use a shared server to perform certain types of database work:

Database management

Backup and restore operation

Batch and batch load operations

Data warehouse operation

Shared servers have the following disadvantages

Generally speaking, we can use the oracle default dedicated server mode, and there is no need to use the shared server mode. One is that we use middleware (such as weblogic) to connect to oracle. The middleware itself has a connection pooling mechanism. In addition, the shared server mode of oracle is not good enough and has many shortcomings.

1) the code path of a shared server is longer than that of a dedicated server, so it is inherently slower than a dedicated server.

2) there is the possibility of artificial deadlock, because it is serial, as long as a connection is blocked, all users on the server process are blocked and deadlock is most likely. ITPUX Technology Network (http://www.itpux.com), China's most professional and comprehensive IT industry technology website.

3) there is the possibility of exclusive transaction, because if the transaction of a session runs for too long, it monopolizes the shared resources, other users can only wait, while the dedicated server, each client is a session.

4) shared server mode limits some database features, such as not starting and shutting down instances separately, not performing media recovery, not using Log Miner, and SQL_TRACE is meaningless (because it is shared rather than the current session).

How do I know if oracle is currently DEDICATED SERVER or SHARED SERVER?

One of the easiest ways to do this is to check the monitor: lsnrctl service

Grid@udevasm:/home/grid] $lsnrctl serviceLSNRCTL for Linux: Version 11.2.0.4.0-Production on 15-JUL-2017 13:07:31Copyright (c) 1991, 2013, Oracle. All rights reserved.Connecting to (DESCRIPTION= (ADDRESS= (PROTOCOL=IPC) (KEY=EXTPROC1521)) Services Summary...Service "+ ASM" has 1 instance (s). Instance "+ ASM", status READY, has 1 handler (s) for this service... Handler (s): "DEDICATED" established:0 refused:0 state:ready LOCAL SERVERService "db01" has 1 instance (s). Instance "udevasm", status READY, has 1 handler (s) for this service... Handler (s): "DEDICATED" established:8 refused:0 state:ready LOCAL SERVERService "udevasm" has 1 instance (s). Instance "udevasm", status READY, has 1 handler (s) for this service... Handler (s): "DEDICATED" established:8 refused:0 state:ready LOCAL SERVERService "udevasmXDB" has 1 instance (s). Instance "udevasm", status READY, has 1 handler (s) for this service... Handler (s): "D000" established:0 refused:0 current:0 max:1022 state:ready DISPATCHER (ADDRESS= (PROTOCOL=tcp) (HOST=udevasm) (PORT=10275)) The command completed successfully

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