oracle performance tuning 12c

oracle performance tuning 12c SQL Tuning The main objective of “Oracle performance tuning”, “SQL tuning” is to avoid performing unnecessary work to access rows that do not affect the result. Scenarios: If a table has huge data, and some SQL queries are taking so much time to execute, what could be the reason? How to tune that query? 1. …

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SQL*Loader

SQL*Loader: SQL Loader is an Oracle database utility, used for data loading from flat-files into the database table. Files used in SQL* Loder are Data_file, Control file, Bad_file, Doscard_file, Log_file.    Data Source: It can be a flat file(data_file) / stdin(standard input) -> file redirect in command prompt while executing sqlldr.    Control file: It gives …

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Oracle Data Redaction

Oracle Data Redaction Oracle Database 12c introduced a new feature related to Advanced Security option which enables the protection of data shown to the user in real-time, without requiring changes to the application. The feature is called Data-redaction. During Data redaction the stored data remain unchanged, while the data to be displayed is transformed on-the-fly before …

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DBMS_REDACT API parameters

DBMS_REDACT API parameters: NameDatatype Value Description Add Policy NONEBINARY_INTEGER 0 No redaction, zero effect on the result of a query against table. FULLBINARY_INTEGER 1 Full redaction, redacts full values of the column data. PARTIALBINARY_INTEGER 2 Partial redaction, redacts a portion of the column data. FORMAT_PRESERVING BINARY_INTEGER 3 Format Preserving RANDOMBINARY_INTEGER 4 Random redaction, each query …

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Oracle nvl2 function

Description: The Oracle NVL2 function extends the functionality of NVL function.  NVL2 function lets you substitutes values for both null and non-null values encountered. Syntax: NVL2( arg1, value_when_not_NULL, value_when_NULL ) arg1:   The string to test for a null value.value_when_not_NULL:   The value returned if string1 is not null.value_when_NULL:   The value returned if string1 …

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SELECT Statement Basics

Basic SELECT Syntax: SELECT   EmpNo, EName    => select_list   /    which columns. FROM       scott.emp;              => data_source /  which table / view / other datasource.  SELECT Query:      It is an operation that retrives data from one or more data sources like: TABLE  / VIEW / MATERIALIZED VIEW. Prerequisites:      The user must have the SELECT priviledges …

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High Level Watermark, PCTFREE and PCTUSED

High Level Watermark(HLW) in datablock: High Level Watermark is a term used with table segment in DB to show the amount of datablock occupied(level) by the table data. As per PCTUSED and PCTFREE mentioned for datablock, the data will fillup in datablocks. When a table created(without data), the High Level Watermark will be on left most datablock(consider the datablocks arrange horizontally). After inserting few records, it fills few datablock, …

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