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March 2010

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 (, and, seems to hit a lot of people, and its root cause are the utilization of wrong hints by the Oracle refresh engine.…