Create a database link Tips
Oracle Tips by Burleson Consulting
January 17, 2008
Question: How to create a database link in
Oracle? What are the options for creating database links?
Answer: Oracle has invested heavily in
distributed database technology and the creation of a database link is very
straightforward. You 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:
Starting in 11g release 2, the syntax has been enhanced to
remove the need to epscify a TNS service_name:
Above we see that the TNS instance name has been replaced
by allowing the server name, port number and Oracle system ID (ORACLE_SID).
You can also create a database link to non-Oracle
Francisco Riccio describes the steps for a database link to MySQL:
Step 1: Your first step is having installed
the TRANSPARENT GATEWAY (it comes in as of the options when you install Oracle).
Step 2: 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:
Step 4: Configure the listener and add the following
(PROGRAM = tg4msql)
(SID_NAME = MSQL)
(ORACLE_HOME = C:\oracle1)
and in our tnsnames.ora add
(ADDRESS = (PROTOCOL = TCP)(HOST = servidor)(PORT = 1521))
(SID = MSQL)
where HS set up as a heterogonous service
Step 5: 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
For more information on database links, see my related notes below:
Get the Complete
Oracle Tuning Details
The landmark book
Tuning: The Definitive Reference Second Edition" has been
updated with over 1,150 pages of expert performance tuning tips.
It's packed with scripts and tools to hypercharge Oracle 11g
performance and you can
buy it for 40% off directly from the publisher.