Re: histogram generation

Take a look at the Oracle Documentation. The Database Performance Tuning Guide and Reference has the following information:

You generate histograms by using the DBMS_STATS package. You can generate histograms for columns of a table or partition. For example, to create a 10-bucket histogram on the SAL column of the emp table, issue the following statement:

EXECUTE DBMS_STATS.GATHER_TABLE_STATS
('scott','emp', METHOD_OPT => 'FOR COLUMNS SIZE 10 sal');

The SIZE keyword declares the maximum number of buckets for the histogram. You would create a histogram on the SAL column if there were an unusually high number of employees with the same salary and few employees with other salaries. You can also collect histograms for a single partition of a table.

Oracle Corporation recommends using the DBMS_STATS package to have the database automatically decide which columns need histograms. This is done by specifying SIZE AUTO.

Hope this helps,

Jeff. Received on Thu Jun 02 2005 - 08:11:05 CDT