Title: Theory / Important / CS / Algo / Database / Oracle / Tuning

Name: Tuning
Definition: Identifying high-load SQL statements
Page: https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/sql-performance-fundamentals.html#GUID-DD9CAA74-3E0B-48C9-8770-AADB614BC992
https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/introduction-to-sql-tuning.html#GUID-B653E5F3-F078-4BBC-9516-B892960046A2
Section: 1
Context: Database
Definition2: Gathering performance-related data
Conjdef: In a deployed application
Definition3: Determining the causes of the problem
Definition4: Defining the scope of the problem
Definition5: Implementing corrective actions for suboptimally performing SQL statements
Definition6: Preventing SQL performance regressions

Name: Proactive tuning
Definition: you regularly use SQL Tuning Advisor to determine whether you can make SQL statements perform better
Page: https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/introduction-to-sql-tuning.html#GUID-B653E5F3-F078-4BBC-9516-B892960046A2
Section: 1.5.1
Context: Database

Name: Reactive tuning
Definition: you correct a SQL-related problem that a user has experienced.
Page: https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/introduction-to-sql-tuning.html#GUID-B653E5F3-F078-4BBC-9516-B892960046A2
Section: 1.5.1
Context: Database

Question: Very broadly, what might be the cause of a performance problem
Answer: Inefficiently designed SQL statements
Page: https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/introduction-to-sql-tuning.html#GUID-B653E5F3-F078-4BBC-9516-B892960046A2
Section: 1.5.1
Context: Database oracle
Answer2: Suboptimal execution plans
Answer3: Missing SQL access structures
Answer4: Stale optimizer statistics
Answer5: Hardware problems

Question: example of inneficient query ?
Answer: Neglecting to add a join condition, which leads to a Cartesian join
Page: https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/introduction-to-sql-tuning.html#GUID-B653E5F3-F078-4BBC-9516-B892960046A2
Section: 1.5.1
Context: Database oracle
Answer2: Using hints to specify a large table as the driving table in a join
Answer3: Specifying UNION instead of UNION ALL
Answer4: Making a subquery execute for every row in an outer query

Name: Hard parse
Definition: A query parsing that requires to compute the execution code.
Page: https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/sql-processing.html#GUID-BFF0B26C-0A5D-4F79-B01E-8E1C4064A6AD
Chapter: II
Section: 3
Context: Database oracle

Name: Soft parse
Definition: A parse that is not a hard parse
Page: https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/sql-processing.html#GUID-BFF0B26C-0A5D-4F79-B01E-8E1C4064A6AD
Chapter: II
Section: 3
Context: Database oracle
Intuition: A query whose code is already in cache

Name: Row source generator
Definition: software that receives the optimal execution plan from the optimizer and produces an iterative execution plan that is usable by the rest of the database
Page: https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/sql-processing.html#GUID-BFF0B26C-0A5D-4F79-B01E-8E1C4064A6AD
Chapter: II
Section: 3
Context: Database oracle

Name: Row source
Definition: a row set returned by a step in the execution plan along with a control structure that can iteratively process the rows
Page: https://docs.oracle.com/en/database/oracle/oracle-database/21/tgsql/sql-processing.html#GUID-BFF0B26C-0A5D-4F79-B01E-8E1C4064A6AD
Chapter: II
Section: 3
Context: Database oracle