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10G默认optimizer_mode为all_rows

原创 IT生活 作者:tsinglee 时间:2007-09-21 17:10:09 0 删除 编辑

show">sys@ora10g>show parameter optimizer_mode

NAME TYPE VALUE
------------------------------------ ----------- ------------------------------
optimizer_mode string all_rows
optimizer_mode establishes the default behavior for choosing an optimization
approach for the instance.
Values:
■ first_rows_n
The optimizer uses a cost-based approach and optimizes with a goal of best
response time to return the first n rows (where n = 1, 10, 100, 1000).
■ first_rows
The optimizer uses a mix of costs and heuristics to find a best plan for fast
delivery
of the first few rows.
■ all_rows
The optimizer uses a cost-based approach for all SQL statements in the session
and
optimizes with a goal of best throughput (minimum resource use to complete the
entire statement).

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