How To Create Database Link

Prerequest:-

DBLink Name

Schema name and password

Connection string(tnsping SID)

Creating Database Link:-

Check DBLink is allreday existist or not

SQL> Select * from dba_db_links where db_link='<db_link_name>';

SQL> CREATE DATABASE LINK <DB_LINK_NAME> CONNECT TO <Schema_name> IDENTIFIED BY <Schema_PWD> USING'TEST=(DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=ebstest.vis.com )(PORT=1521)) (CONNECT_DATA=(SERVICE_NAME=test)(INSTANCE_NAME=test)))';

If you want to recreate a DB Link first get the source code from the database link before you drop the DBLink

SQL>set long 1000

SQL> select DBMS_METADATA.GET_DDL('DB_LINK','DB.DBLINK,'DB.OWNER') from dba_db_links;

Connectivity Test:-

select * from global_name@<DB_LINK_NAME>

select * from global_name;

Drop DB Link:

Check the DB link and respective user and connect the user drop the db link 

SQL> set lines 1000

col owner for a20

col username for a20

col host for a40

col db_link for a30

col create for a10

SQL> select * from dba_db_links;

SQL> Select * from dba_db_links where db_link='<D_LINK_NAME>';

SQL> Drop database link <DB_LINK_NAME>;