Why is a FAST Refresh of Remote Materialized View Doing Updates While There Are Inserts ONLY on the Master Table (Doc ID 2272257.1)

Last updated on JULY 13, 2017

Applies to:

Oracle Database - Enterprise Edition - Version 12.1.0.2 and later
Information in this document applies to any platform.

Symptoms

Problem Description
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You have a materialized view which selects from a table across a dblink to a master database. The FAST refresh of the materialized view is running for a very long time. The session running the refresh is spending most of it's time running an update statement. It shouldn't be doing any updates because the materialized view log contains only inserts. The updates appear to be doing nothing for the most part.  

Eventually after wasting most of its time on millions of updates, it does the inserts and finishes successfully after several hours. How do you prevent it from doing the updates in the first place? It should only be inserting new rows.

Cause

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