This
syntax is described in your Oracle SQL reference documentation.
Testing the Effect of New Statistics
There may be times when you don??™t want to update your statistics, such as when the
distribution of data in your database has reached a steady state or when your queries
are already performing optimally (or at least deliver adequate, consistent performance).
Oracle gives youa way youcan try out a new set of statistics to see if they
might make things better while still maintaining the option of returning to the old set:
youcan save your statistics in a separate table and then collect new ones. If, after testing
your application with these new statistics, you decide you preferred the way the old
statistics worked, you can simply reload the saved statistics.
114 | Chapter 4: Oracle Data Structures
Influencing the cost-based optimizer
There are two ways youcan influence the way the cost-based optimizer selects an
execution plan. The first way is by setting the OPTIMIZER_MODE initialization
parameter. ALL_ROWS is the default setting for OPTIMIZER_MODE enabling
optimization with the goal of best throughput.
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