A database link is a pointer that defines a one-way communication path from an Oracle Database server to another database server. The link pointer is actually defined as an entry in a data dictionary table. A database link is a schema object in one database that enables you to access objects on another database.
To create a private database link, we must have the create database link system privilege. To create a public database link, we must have the create public database link system privilege. Also, we must have the CREATE SESSION system privilege on the remote Oracle database . Before creating it, we must collect the following information:
1.) A net service name that our local database instance can use to connect to the remote instance and2.) A valid username and password on the remote database.
The net service name is necessary for every database link. The username and password that we specify when defining a database link are used to establish the connection to the remote instance. The Credentials of database links are :
Primary Server = Noida
Remote Server = Delhi 1.) Connect to datbase as
C:\> sqlplus sys/xxxx@delhi as sysdba
2.) Create a user
SQL> create user abc identified by abc
2 default tablespace users
3 quota unlimited on users;
User created.
3.) Grant the privileges required for database link
SQL> grant create public database link , create session, create table to abc;
Grant succeeded.
4.) Connect with "ABC" user and create a table for testing purpose as
SQL> conn abc/abc@delhi
Connected.
SQL> create table test1 (id number);
Table created.
SQL> insert into test1 values(&T);
Enter value for t: 23
old 1: insert into test1 values(&T)
new 1: insert into test1 values(23)
1 row created.
SQL> /
Enter value for t: 345
old 1: insert into test1 values(&T)
new 1: insert into test1 values(345)
1 row created.
SQL> /
Enter value for t: 32
old 1: insert into test1 values(&T)
new 1: insert into test1 values(32)
1 row created.
SQL> commit ;
Commit complete.
SQL> select * from test1 ;
ID
----------
23
345
32
SQL> exit
5.) Connect with primary database as
c:\>sqlplus sys/XXXX@noida as sysdba
6.) Create a Public database link and access the remote table(test1) as
SQL> create public database link d_link connect to abc identified by abc using 'DELHI' ;
Database link created
SQL> select * from abc.test1@d_link ;
ID
----------
23
345
32
Hence , we access the remote table by using the database link .
Enjoy :-)
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