Default optimizer in oracle 10g

The default optimizer costing in Oracle 10g is cpu, and you can change to io costing by using these techniques: Make sure that optimizer_index_cost_adj is set to the default value (Oraclebug ) Add a "no_cpu_costing" hint in your SQL. alter session set "_optimizer_cost_model"=io;. Optimizer to estimate the cardinality, and allows it to generate a more accurate execution plan. Oracle automatically determines the columns that need histograms based on the column usage information (strumentidigitali.com_USAGE$), and the presence of a data skew. For example, Oracle will not. In Oracle 11g, there has been a restructuring of the job scheduling framework. In particular, the automatic gathering of optimizer statistics. In Oracle 10g, the following query reveals the association of the program GATHER_STATS_PROG with a job GATHER_STATS_JOB. In Oracle 11g, that association does not seem to be present as the query returns.

Default optimizer in oracle 10g

In Oracle 11g, there has been a restructuring of the job scheduling framework. In particular, the automatic gathering of optimizer statistics. In Oracle 10g, the following query reveals the association of the program GATHER_STATS_PROG with a job GATHER_STATS_JOB. In Oracle 11g, that association does not seem to be present as the query returns. Upgrade From 9i OPTIMIZER_MODE RULE Or CHOOSE No Longer Used In 10g And Higher: Use ALL_ROWS Or FIRST_ROWS _n (Doc ID ) Last updated on AUGUST 04, Applies to: Oracle Database - Enterprise Edition - Version to [Release to ] Information in this document applies to any platform. May 11,  · CHOOSE: Oracle's default optimizer mode is called CHOOSE. In the CHOOSE optimizer mode, Oracle will execute the rule-based optimizer if there are no statistics present for the table, or execute the cost-based optimizer if statistics are present. The default optimizer costing in Oracle 10g is cpu, and you can change to io costing by using these techniques: Make sure that optimizer_index_cost_adj is set to the default value (Oraclebug ) Add a "no_cpu_costing" hint in your SQL. alter session set "_optimizer_cost_model"=io;. On Oracle 10g: Execution Plan 0 SELECT STATEMENT Optimizer=ALL_ROWS (Cost=16 Card=22 Bytes=) 1 0 HASH JOIN (OUTER) (Cost=16 Card=22 Bytes=) 2 1 TABLE ACCESS (BY INDEX ROWID) OF 'MASTERTABLE' (TABLE) (Cost=5 Card=22 Bytes=).The Optimizer uses costing methods, cost-based optimizer (CBO), or internal rules, . The OPTIMIZER_MODE initialization parameter establishes the default. REM ok, that is inherited, haven't set optimizer mode for my session. REM so far . you do not, until 10g SQL> desc V$SES_OPTIMIZER_ENV Name Null?. Optimizer defaults are adequate for most operations, but not all. Nov 21, In choose mode, the optimizer will be closer to an all_rows optimization. Oracle will use CBO and optimizer_mode set to FIRST_ROWS or .. and on 10g OPTIMIZER_MODE = all_rows which is default optimizer of 10g. The optimizer is built-in software that determines the most efficient way to execute a . For example, the internal default for an equality predicate (last_name.

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Why do you need the Oracle Database Optimizer?, time: 1:50
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3 thoughts on “Default optimizer in oracle 10g

  • 28.04.2010 at 00:56
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