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Service Name [message #674075]

Wed, 02 January 2019 14:20

wtolentino
Messages: 421
Registered: March 2005

Senior Member

in the Oracle Database Concepts 12c Release 1 (12.1) E41396-15 manual, Figure 16-7 (page 16-14) https://docs.oracle.com/database/121/CNCPT/dist_pro.htm#GUID-C931A159-E1FE-4DB3-A811-510C42516683__CHDFGAED

/foru/forum/fa/13989/0/

it shows that one single-instance database is associated with two services and they are book.example.com and soft.example.com.

1. an instance by definition is a set of Oracle background processes/threads and a shared memory area. is the service name an alias to the instance?

2. how would that be interpreted in TNS entries is it

book.example.com =
(DESCRIPTION = 
  (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = myHostname)(PORT = 1521)))  
  (CONNECT_DATA = (SERVICE_NAME = book.example.com)(SID = book)(SERVER = DEDICATED))
)

soft.example.com =
(DESCRIPTION = 
  (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = myHostname)(PORT = 1521)))  
  (CONNECT_DATA = (SERVICE_NAME = soft.example.com)(SID = book)(SERVER = DEDICATED))
)

book.example.com, soft.example.com =
(DESCRIPTION = 
  (ADDRESS_LIST = (ADDRESS = (PROTOCOL = TCP)(HOST = myHostname)(PORT = 1521)))  
  (CONNECT_DATA = (SERVICE_NAME = book.example.com)(SID = book)(SERVER = DEDICATED))
)

thank you.

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Re: Service Name [message #674076 is a reply to message #674075]

Wed, 02 January 2019 15:42

Michel Cadot
Messages: 68716
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

There are 2 notions of "service name": network service name which is a tnsnames.ora entry and database service name which enables to direct connections on some instances with RAC or to trace application on RAC or not. See DBMS_SERVICE and the link in this page for RAC service administration (using srvctl).

If you use service names, you don't need SID parameter in your tnsnames.ora entry (unless you want to access the service on a specific instance).

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Re: Service Name [message #674083 is a reply to message #674075]

Thu, 03 January 2019 01:50

John Watson
Messages: 8960
Registered: January 2010
Location: Global Village

Senior Member

You have hit on (in my opinion) one of the worst bits of Oracle's documentation. The description and diagrams imply that a browser client can communicate directly with a database using http, which is wrong. Forget that whole section of the docs. It works like this:

The client (an OCI client, not a browser) contacts the listener using TCP (not http) requesting a connection to a service. The listener determines which instance is offering that service, and launches a server process from the ORacle home of that instance. It then connects the client to the process (various methods for this, platform and version dependent). The established session is thus a client talking to a remote server process over TCP, and the server process working with the memory structures that are the local instance.

Improvements or corrections welcome.

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