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materialized views

fast refresh of join-only MVs: _mv_refresh_use_stats and locking log stats

A devastating performance degradation of materialized view fast refreshes can happen in versions after 9i - and can be healed rather easily by simply setting the hidden parameter _mv_refresh_use_stats or, a bit surprisingly, by locking statistics on the logs. The problem can manifest at least in the currently-latest patchsets of 10g, 11gR1 and 11gR2 (10.2.0.4, 11.1.0.7 and 11.2.0.1), seems to hit a lot of people, and its root cause are the utilization of wrong hints by the Oracle refresh engine.

We will investigate the join-only MV case only, since this is the case I have investigated after a question by Christo Kutrovsky, factoring in some observations by Taral Desai and some Support notes; I have some clues that something similar may happen for other types of MVs.

11gR2: new algorithm for fast refresh of on-commit materialized views

This post investigates the improvements that have been made in 11gR2 to the fast refresh engine of materialized views (MVs) that are set to be automatically refreshed at commit time. We speak about join-only materialized views only in this post, as always with the help of a test case.
As noted in the post of mine [...]

11gR2: materialized view logs changes

In this post we are going to discuss some 11gR2 changes to materialized view logs that are aimed at increasing the performance of the fast-refresh engine of materialized views (MVs), especially the on-commit variant.
The MV logs, in 10gr2, now comes in two flavours: the traditional (and still the default) timestamp-based one and the brand [...]