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Category: Oracle

Oracle

Oracle performance

Flush Bad SQL Plan from Shared Pool

Bulent Soylu April 5, 2023 execution planoracle

Sometimes it is required to flush the BAD SQL_PLAN from shared_pool so that new (or old) better execution plan can be picked by SQL_ID 1)…

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Oracle performance

Oracle CBO is ignoring SYS_DL_CURSOR

Bulent Soylu April 4, 2023 append_valueshintsoracleperformancesys_dl_cursor

Some days ago i came across with a pl/sql code where they used (for some reason) an Oracle hint called SYS_DL_CURSOR. I got it when i…

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Oracle performance

APPEND_VALUES and SYS_DL_CURSOR Hints with HCC

Bulent Soylu April 4, 2023 append_valueshintsinformaticaoracleperformancesys_dl_cursor

The APPEND_VALUES hint was introduced in 11.2 to allow direct path inserts with variables using the VALUES clause. i.e. INSERT INTO XYZ (COL1, COL2) VALUES…

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Oracle

How to Increase MEMORY_TARGET

Bulent Soylu March 30, 2023 memorymemory_targetoraclesga

Before you can increase memory in oracle database, you must first understand four oracle memory parameters which govern the instance. SGA_TARGET and SGA_MAX_SIZE MEMORY_TARGET and…

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Oracle performance

Adaptive Cursor Sharing in Oracle Database 11g Release 1

Bulent Soylu March 28, 2023 adaptive cursor sharingbind variablescursor sharingoracle

DBAs are always encouraging developers to use bind variables, but when bind variables are used against columns containing skewed data they sometimes lead to less…

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Oracle performance

How to Swap SQL_Profiles?

Bulent Soylu February 2, 2023 11goracleperformancequery optimizersql profiles

The central idea behind “swapping” SQL profiles is simple.  You define a SQL profile that specifies the SQL statement that you want to tune, and an…

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Oracle performance

SQL Profiles in the Data Dictionary

Bulent Soylu February 2, 2023 oracleperformancequery optimizersql profiles

In the paper SQL Profiles (page 22) I described the data dictionary tables where the hints belonging to SQL profiles are stored. For example, with the following…

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Oracle performance

Useful Gather Statistics Commands In Oracle

Bulent Soylu January 31, 2023 DBMS_STATSgather_statsoracleperformance

This article contains all the useful gather statistics related commands. 1. Gather dictionary stats: — It gathers statistics for dictionary schemas ‘SYS’, ‘SYSTEM’ and other…

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Oracle performance

CURSOR_SHARING=SIMILAR AND FORCE – SOME EXAMPLES

Bulent Soylu January 29, 2023 cursor_sharingoracleperformance

The CURSOR_SHARING parameter basically influences the extent to which SQL statements (or cursors) can be shared.  The possible values are EXACT which is the default…

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Oracle performance

12c: Optimizer_Dynamic_Sampling = 11

Bulent Soylu January 22, 2023 dynamic_samplingoracleoracle 12cperformance

With default sampling level of 2 (from 10g onwards) , dynamic sampling is performed only for the objects for which statistics do not exist. If…

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