Create Database Link Oracle

Create Database Link Oracle

The creation of a database link in Oracle straightforward.  To create a database link in Oracle, specify the database link name, the remote user to connect to, the password for the remote user and the TNS service name for the database link connection:

create public database link
  mylink
connect to
  remote_username
identified by
  mypassword
using 'tns_service_name';

You can also create a database link in Oracle to non-Oracle databases,  Francisco Riccio describes the steps for a database link to MySQL:

Step 1:  Your first step to creating a database link in Oracle to a non-Oracle database is having installed the TRANSPARENT GATEWAY (it comes in as one of the options when you install Oracle).

Step 2: To create a database link in Oracle to a non-Oracle database, you must have a user in the SQL Server.

Step 3: In the directory <ORACLE_HOME>\tg4msql\admin look for the file inittg4msql.ora and have the following options:

HS_FDS_CONNECT_INFO="SERVER=name_server;DATABASE=name_db"
HS_FDS_TRACE_LEVEL=OFF
HS_FDS_RECOVERY_ACCOUNT=user_sqlserver
HS_FDS_RECOVERY_PWD=pass_user_sqlserver

Step 4: Configure the listener and add the following

(SID_DESC =
(PROGRAM = tg4msql)
(SID_NAME = MSQL)
(ORACLE_HOME = C:\oracle1)
)
)

and in our tnsnames.ora add

MSQL=
(DESCRIPTION =
(ADDRESS_LIST =
(ADDRESS = (PROTOCOL = TCP)(HOST = servidor)(PORT = 1521))
)
(CONNECT_DATA =
(SID = MSQL)
)
(HS=OK)
)

where HS set up as a heterogonous service

Step 5: The last step to creating a database link in Oracle to a non-Oracle database is to create a link to sql server.

create database link msql connect to user_sqlserver identified by password using 'MSQL';

Step 6: You can now use the database link to a foreign database:

select * from table@msql

 

 

 

 

 

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