John Smiley wrote:
John, with all due respect, she was asking about the differences in the access path of a query, not how toHi Patty,
When you gather/import system statistics, you provide the CBO with more information about your system and allows it to use CPU costing as well as I/O costing. System stats should be gathered while the system is under the type of load you want to use the stats for. If you have differing loads (say transaction processing during the day and batch processing at night), you may want to have more than one set of system stats to fit the load.
-- Mladen Gogala Oracle DBA Ext. 121