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I have a couple of nested materialized views that fast refresh. They worked fine in Oracle 11g but since upgrading to Oracle 12c (12.1.0.2.0 on Solaris) I am occasionally getting duplicate rows (the rows are not identical, usually some data has changed - I suspect the duplicates reflect the before and after change state). If I subsequently do a complete refresh the duplicate rows disappear.

I have My Oracle Support access but I haven't been able to find any bugs that I can tie to this behaviour.

I am aware of new out-of-place refreshes that have been added to Oracle 12c. The documentation says of the out-of-place functionality (edited for brevity).

It helps to avoid potential problems such as ... intermediate refresh results being seen.

Are "intermediate refresh results" what I am seeing now? (I didn't before).

Is anyone aware of any relevant issues/bugs/patches?

  • Just curious, Are you aware of any direct data load operations (impdp, insert /*+append */, etc...) that may be happening on the source tables? Direct data load doesn't update the mview logs, so we complete refresh any affected mviews after such an operation due to the possibility of duplicate rows and/or missing data in the mview. – Kris Johnston Aug 3 '16 at 16:30
  • I am not aware of any direct data load operations on the source tables. The source tables should only experience standard DML operations (insert, update, etc.). – Mark McLaren Aug 3 '16 at 17:01

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