There is a well-documented problem relating to DBMS_STATS.COPY_TABLE_STATS between partitions where high/low values of the partitioning key column were just copied verbatim from the source partition. This particular problem has now been patched (see 8318020.8). For background, see Doug Burns’ blog and his excellent paper which covers the whole topic of statistics on partitioned tables. This post Maintaining statistics on large partitioned tables on the Oracle Optimizer blog details what the dbms_stats.

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Chucking a stick in the spokes of your carefully-tested ETL/BI … My opinion is that automated stats gathering for non-system objects should be disabled on Oracle Data Warehouses across all environments. All it does it cover up poor design or implementation which has omitted to consider statistics management. Once you get into the realms of millions or billions of rows of data, the automated housekeeping may well not have time to stat all of your tables on each run.

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This is a series of posts where I hope to humbly plug some gaps in the information available (or which has escaped my google-fu) regarding statistics management in Oracle 11g specific to Data Warehousing. Incremental Global Statistics is new functionality in Oracle 11g (and 10.2.0.4?) and is explained in depth in several places including: Oracle® Database Performance Tuning Guide - Statistics on Partitioned Objects Greg Rahn - Oracle 11g: Incremental Global Statistics On Partitioned Tables Inside the Oracle Optimiser - Maintaining statistics on large partitioned tables Amit Poddar - One Pass Distinct Sampling (ppt - slides 52 onwards are most relevant) In essence, Oracle maintains information about each partition when statistics is gathered on the partition, and it uses this to work out the global statistics - without having to scan the whole table.

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