Re: question regarding statistics
- From: Mladen Gogala <mgogala@xxxxxxxxxxxxxxxxxxxx>
- To: bunjibry@xxxxxxxxx
- Date: Mon, 07 Mar 2005 13:38:59 -0500
Bryan Wells wrote:
>i may have asked this once before, so if it is indeed redundant i appologize:
>
>is there a difference in analyze and compute statistics?
>
>
You probably mean whether there is adifference between DBMS_STATS and
analyze. There are several,
differences and we can divide them in two groups:
1) Performance differences
DBMS_STATS can utilize PQ. Analyze can not.
2) Essential differences
DBMS_STATS package can gather global statistics at multiple
levels as specified by the granularity parameter.
In contrast, the legacy ANALYZE command collects statistics
only at the lowest level and derives higher level
statistics by aggregation.
These aggregated statistics are sometimes less accurate than
the global statistics since it is not possible to
precisely determine the overlap of values across partitions.
Statistics for the number of distinct values and
density are particularly susceptible to inaccuracy
DBMS_STATS can populate auxiliary statistics, needed for CPU
costing. Analyze can not.
More detail in Note:114671.1
--
Mladen Gogala
Oracle DBA
Ext. 121
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