1.244 OPTIMIZER_MODE
OPTIMIZER_MODE
establishes the default behavior for choosing an optimization approach for the instance.
Property | Description |
---|---|
Parameter type |
String |
Syntax |
|
Default value |
|
Modifiable |
|
Modifiable in a PDB |
Yes |
Basic |
No |
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 (wheren
= 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.
FIRST_ROWS
is available for backward compatibility and plan stability; useFIRST_ROWS_
n instead. -
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).
See Also:
-
Oracle Database SQL Tuning Guide for more information on setting this parameter
-
Oracle Database Concepts and Oracle Database SQL Tuning Guide for more information about the optimizer