How to Create a Materialized View Log in Oracle

Learn how to create a materialized view log in Oracle to improve data replication and performance in your database environment.
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Materialized views (also known as snapshots) are a way to improve query performance by creating copies of data that can be refreshed periodically. Materialized view logs, on the other hand, are used to track changes made to tables so that materialized views can be incrementally refreshed instead of fully rebuilt each time. In this guide, we will go through the steps to create a materialized view log in Oracle.

What is a Materialized View Log?

A materialized view log is a mechanism in Oracle that tracks changes to a table. When changes occur, the log records information about these changes so that materialized views based on the table can be updated incrementally.

Creating a Materialized View Log in Oracle

To create a materialized view log in Oracle, follow these steps:

Choose the Table: Identify the table for which you want to create a materialized view log. This table should be the source of the data that will be tracked.

Create the Log: Use the CREATE MATERIALIZED VIEW LOG statement to create a materialized view log for the chosen table. The statement allows you to specify which columns you want to track and whether you want the log to include new values for updated rows.

Here's an example statement:

[[See Video to Reveal this Text or Code Snippet]]

Replace your_table_name with the name of your table and specify the columns you want to track. You can include additional clauses such as INCLUDING NEW VALUES if you want to track both old and new values of the specified columns.

Permissions: Make sure you have the necessary permissions to create a materialized view log on the table. The user must have the ALTER permission on the table.

Verify: After creating the materialized view log, verify that it has been created successfully. You can check the database's data dictionary views, such as DBA_MVIEW_LOGS or ALL_MVIEW_LOGS, to confirm.

Refresh the Materialized View: Once the materialized view log is set up and changes are being tracked, you can use the information in the log to refresh your materialized views efficiently.

Conclusion

Creating a materialized view log in Oracle is a straightforward process that can greatly improve data replication and performance in your database environment. By using the log to track changes in your tables, you can incrementally refresh materialized views and keep your data up-to-date while minimizing the impact on performance.