Basic Replication -- 8 : REFRESH_MODE ON COMMIT

So far, in previous posts in this series, I have demonstrated Materialized Views that set to REFRESH ON DEMAND.

You can also define a Materialized View that is set to REFRESH ON COMMIT -- i.e. every time DML against the Source Table is committed, the MV is also immediately updated.  Such an MV must be in the same database  (you cannot define an ON COMMIT Refresh across two databases  -- to do so, you have to build your own replication code, possibly using Database Triggers or external methods of 2-phase commit).

Here is a quick demonstration, starting with a Source Table in the HEMANT schema and then building a FAST REFRESH MV in the HR schema.

SQL> show user
USER is "HEMANT"
SQL> create table hemant_source_tbl (id_col number not null primary key, data_col varchar2(30));

Table created.

SQL> grant select on hemant_source_tbl to hr;

Grant succeeded.

SQL> create materialized view log on hemant_source_tbl;

Materialized view log created.

SQL> grant select on mlog$_hemant_source_tbl to hr;

Grant succeeded.

SQL>
SQL> grant create materialized view to hr;

Grant succeeded.

SQL> grant on commit refresh on hemant_source_tbl to hr;

Grant succeeded.

SQL>
SQL> grant on commit refresh on mlog$_hemant_source_tbl to hr;

Grant succeeded.

SQL>

Note : I had to grant the CREATE MATERIALIZED VIEW privilege to HR for this test case. Also, as the MV is to Refresh ON COMMIT, two additional object-level grants on the Source Table and the Materialized View Log are required as the Refresh is across schemas.

SQL> connect hr/HR@orclpdb1
Connected.
SQL> create materialized view hr_mv_on_commit
  2  refresh fast on commit
  3  as select id_col as primary_key_col, data_col as value_column
  4  from hemant.hemant_source_tbl;

Materialized view created.

SQL>

Now that the Materialized View is created successfully, I will test DML against the table and check that an explicit REFRESH call (e.g. DBMS_MVIEW.REFRESH or DBMS_REFRESH.REFRESH) is not required.

SQL> connect hemant/hemant@orclpdb1
Connected.
SQL> insert into hemant_source_tbl values (1,'First');

1 row created.

SQL> commit;

Commit complete.

SQL> select * from hr.hr_mv_on_commit;

PRIMARY_KEY_COL VALUE_COLUMN
--------------- ------------------------------
              1 First

SQL> connect hr/HR@orclpdb1
Connected.
SQL> select * from hr_mv_on_commit;

PRIMARY_KEY_COL VALUE_COLUMN
--------------- ------------------------------
              1 First

SQL>

The Materialized View in the HR schema was refreshed immediately, without an explicit REFRESH call.

Remember : An MV that is to REFRESH ON COMMIT must be in the same database as the Source Table.