Hi

Here's an example 

Let Node1 be the master instance and Node2  is the materialized view site.

1)First we must check that the user who will own the materialized views has the correct privileges:

CONNECT sys@Node2
GRANT CREATE DATABASE LINK TO scott;
GRANT CREATE MATERIALIZED VIEW TO scott;

2)CONNECT scott/tiger@Node2

CREATE DATABASE LINK Node1.WORLD CONNECT TO scott IDENTIFIED BY tiger USING 'Node1.WORLD';

CREATE MATERIALIZED VIEW emp_mv
BUILD IMMEDIATE 
REFRESH FORCE
ON DEMAND
AS
SELECT * FROM emp@Node1.world;

BEGIN
  Dbms_Stats.Gather_Table_Stats(
    ownname => 'SCOTT',
    tabname => 'EMP_MV');
END;
/
The FORCE parameter means the materialized view will attempt a FAST refresh. If this cannot be performed a COMPLETE refresh will occur.

We then create a refresh group which is defined to refresh every minute and assign our materialized view to it:

BEGIN
   Dbms_Refresh.Make(
     name => 'SCOTT.MINUTE_REFRESH',
     list => '',
     next_date => SYSDATE,
     interval => '/*1:Mins*/ sysdate + 1/(60*24)',
     implicit_destroy => FALSE,
     lax => FALSE,
     job => 0,
     rollback_seg => NULL,
     push_deferred_rpc => TRUE,
     refresh_after_errors => TRUE,
     purge_option => NULL,
     parallelism => NULL,
     heap_size => NULL);
END;
/

BEGIN
   Dbms_Refresh.Add(
     name => 'SCOTT.MINUTE_REFRESH',
     list => 'SCOTT.EMP_MV',
     lax => TRUE);
END;
/
At this point the materialized view is created and will refresh every minute.

3) Next , Create Remote Objects.

Since the refresh involves truncating the materialized view table and repopulating it completely, it can be quite time consuming an involve a considerable amount of network traffic. To reduce the replication costs all changes to the base table since the last refresh can be stored in materialized view logs. With this data a FAST refresh only needs to apply the changes rather than a COMPLETE refresh of the materialized view.

To take advantage of the of the FAST refresh we must connect to the master instance and create the materialized view log:

CONNECT scott/tiger@Node1

CREATE MATERIALIZED VIEW LOG ON scott.emp
TABLESPACE users
WITH PRIMARY KEY
INCLUDING NEW VALUES;