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Cubes are updated in a batch window at regular intervals: weekly, daily, or periodically throughout the day. Some administrators refresh their data by adding periods to the time dimension of a measure, and may also roll off an equal number of the oldest time periods. Each update provides a fixed historical record of a particular business activity for that interval. Other administrators do a full rebuild of their data rather than performing incremental updates.
Table: Refresh Methods For Cube Materialized Views describes the refresh methods that are supported on cube materialized views.You can specify the COMPLETE
, FAST
, or FORCE
methods for refreshing a cube. The materialized view subsystem invokes two additional methods, FAST_PCT
and FAST_SOLVE
. They are not separate choices.
Refresh Methods For Cube Materialized Views
Refresh Method | Description |
---|---|
|
Deletes and recreates the cube. This option supports arbitrarily complex mappings from the source tables to the cube. |
|
Loads and re-aggregates only changed values, based on the materialized view logs or, after direct path loading, on the ALL_SUMDELTA data dictionary view. The source for the refresh is the incremental differences that have been captured in the materialized view logs, rather than the original mapped sources. These differences are used to incrementally rebuild the cube. Only cells that are affected by the changed values are re-aggregated. This option supports only simple mappings for cube materialized views, that is, where no expressions (other than table.column), views, or aggregations occur in the query defining the mapping. The materialized view subsystem determines whether to perform a |
|
Loads and re-aggregates data only from changed partitions. This method works best when the source table and the cube are partitioned on the same dimension.
|
|
Loads and re-aggregates only changed values, based on the original mapped data source.
This option is supported for arbitrarily complex mappings from the source tables to the cube. To discover whether a |
|
Loads and re-aggregates values using the best method possible. When a |
The build log lists the CLEAR LEAVES
command when the FAST SOLVE
method was used. Example: Identifying a FAST SOLVE Refresh shows the rows of CUBE_BUILD_LOG
concerned with building UNITS_CUBE
.
Identifying a FAST SOLVE Refresh
SELECT build_object, status, command FROM cube_build_log WHERE build_object='UNITS_CUBE' AND build_id=8; BUILD_OBJECT STATUS COMMAND ------------ ---------- ------------------------- UNITS_CUBE STARTED COMPILE AGGMAP UNITS_CUBE COMPLETED COMPILE AGGMAP UNITS_CUBE STARTED UPDATE UNITS_CUBE COMPLETED UPDATE UNITS_CUBE STARTED CLEAR LEAVES UNITS_CUBE COMPLETED CLEAR LEAVES UNITS_CUBE STARTED LOAD UNITS_CUBE COMPLETED LOAD UNITS_CUBE STARTED SOLVE UNITS_CUBE COMPLETED SOLVE UNITS_CUBE STARTED UPDATE UNITS_CUBE COMPLETED UPDATE UNITS_CUBE STARTED ANALYZE UNITS_CUBE COMPLETED ANALYZE 14 rows selected.