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-> Oracle Shared vs. Dedicated Server Architecture

 

 Oracle Shared vs. Dedicated Server Architecture 

 

 

Questions:

  1. Which is the main difference between a MTS (Shared Server) and Dedicated Server?

  2. Is is possible to have MTS and Dedicated Servers in the same time for the same database?

  3. How could I know if the database use a Shared Server architecture?

  4. How could I set up a Shared Server?

  5. Is it possible to over ride the "by default" behavior of the database regarding MTS/ Dedicated Server architecture?

  6. How could I disable a Shared (MTS) Server Architecture?

1.  Which is the main difference between a MTS (Shared Server) and Dedicated Server?

 

In a Shared Server architecture MANY sessions (user connections) have ONE server process associated.

In a Dedicated Server architecture ONLY ONE sessions (user connections) have ONLY ONE server process associated.

Because a Shared Server architecture use a multi-thread architecture (one server process has more threads), a Shared Server is named MTS (Multi-Thread Server) as well.

 

 

2.  Is is possible to have MTS and Dedicated Servers in the same time for the same database?

 

Yes, is possible. A database could be configured to have both architecture in the same time. However, because the RAM memory is not longer a big constraint, the Dedicated Server Architecture must be used as general rule.  

 

 

3.  How could I know if the database use a Shared Server architecture?

 

The following select give us the response:  SELECT sid, username, server FROM v$session WHERE type='USER';

 

Oracle shared vs. dedicated architecture

 

However a dispatcher could be configured and running even if is not used (the dispatcher is used by the MTS architecture ONLY). To see if a dispatcher is used, that means to see if a dispatcher process was created, we have to run the following select:

 

SELECT * FROM v$dispatcher;

 

Oracle shared vs. dedicated architecture

 

 

4.  How could I set up a Shared Server?

 

This is possible by adding the following line in the init.ora: 

DISPATCHERS = '(ADDRESS=(PROTOCOL=TCP)(HOST=<host_name>)(PORT=<port_name>))'

 

There are some optional attributes which can be included in the DISPATCHERS parameter: CONNECTIONS, DISPATCHERS,  LISTENER, MULTIPLEX,  SERVICE, SESSIONS, MAX_DISPATCHERS,  SHARED_SERVERS, 

MAX_SHARED_SERVER, etc.

 

ATTENTION: The listener must be started when the database is starting up, because during the database startup the dispatcher is registered with the listener.

 

 

5.  Is it possible to over ride the "by default" behavior of the database regarding MTS/ Dedicated Server architecture?

 

Yes, only if a dispatcher process is running in the database. This is done by configuring the tnsnames.ora file on the client side.

 

   tnsnames.ora which force the client to use the DEDICATED architecture even if a DISPATCHER is configured for the database:

 

DB10 =

(DESCRIPTION =

      (ADDRESS = (PROTOCOL = TCP)(HOST = cata1)(PORT = 1521))

(CONNECT_DATA = (SERVICE_NAME = db10) (SERVER = DEDICATED) )

)

 

6.  How could I disable a Shared (MTS) Server Architecture?

 

a) modify the initialization file (init<SID>.ora, or the spfile) : remove the DISPATCHERS parameter. 

b) assure that the tnsnames.ora on the client side use "(SERVER = DEDICATED)" instead "(SERVER = MTS)" 

c) stop the listener

d) stop the database

e) start the listener

f)  start the database

 

 

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