Mview log is needed for mview fast refresh.It records every changed row.But for Partition Maintenance Operations (PMOPS) such as alter partition, drop partition, truncate partition, etc, the mview log does't record these information.In order to keep the materialized view consistence with master table(or base table) and avoid complete refresh,since Oracle server version 9i,Oracle can take advantage of PCT (Partition Change Tracking) mechanism to do a fast_pct refresh.
Although fast_pct refresh will not refresh all rows of a table,it will refresh all rows related to the changed partitions.
But there are some limitations of fast_pct.PCT is not supported over database links.If the materialized view is distributed (i.e. the master table and the materialized view are located on different databases) then an ORA-12034( Materialized View Log Younger than Last Refresh) error is expected after PMOPS to force a complete refresh. Another limitation is the top level partition key must consist of only a single column.

ITPub博客

Limitation of PCT (Partition Change Tracking)

最新文章