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venerdì, luglio 22, 2011

SQL Tuning Sets

A SQL Tuning Set (STS) is a database object that includes one or more SQL statements along with their execution statistics and execution context, and could include a user priority ranking. The SQL statements can be loaded into a SQL Tuning Set from different SQL sources, such as the Automatic Workload Repository, the cursor cache, or custom SQL provided by the user.

An STS includes:
  • A set of SQL statements
  • Associated execution context, such as user schema, application module name and action, list of bind values, and the cursor compilation environment
  • Associated basic execution statistics, such as elapsed time, CPU time, buffer gets, disk reads, rows processed, cursor fetches, the number of executions, the number of complete executions, optimizer cost, and the command type
  • Associated execution plans and row source statistics for each SQL statement (optional)
A SQL Tuning Set can be used as input to the SQL Tuning Advisor, which performs automatic tuning of the SQL statements based on other input parameters specified by the user. SQL Tuning Sets are transportable across databases and can be exported from one system to another, allowing for the transfer of SQL workloads between databases for remote performance diagnostics and tuning. To transport SQL Tuning Sets, use the DBMS_SQLTUNE package procedures.

(Performance Tuning Guide - Ch12.9)

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