12 Automatic SQL Tuning

This chapter discusses Oracle automatic SQL tuning features.

This chapter contains the following sections:

12.1 Automatic SQL Tuning Overview

Automatic SQL Tuning is a new capability of the query optimizer that automates the entire SQL tuning process. Using the newly enhanced query optimizer to tune SQL statements, the automatic process replaces manual SQL tuning, which is a complex, repetitive, and time-consuming function. The Automatic SQL Tuning features are exposed to the user with the SQL Tuning Advisor.

This section covers the following topics:

12.1.1 Query Optimizer Modes

The enhanced query optimizer has two modes: Normal mode

In normal mode, the optimizer compiles the SQL and generates an execution plan. The normal mode of the optimizer generates a reasonable execution plan for the vast majority of SQL statements. Under normal mode the optimizer operates with very strict time constraints, usually a fraction of a second, during which it must find a good execution plan. Tuning mode

In tuning mode, the optimizer performs additional analysis to check whether the execution plan produced under normal mode can be further improved. The output of the query optimizer is not an execution plan, but a series of actions, along with their rationale and expected benefit for producing a significantly superior plan. When called under the tuning mode, the optimizer is referred to as the Automatic Tuning Optimizer. The tuning performed by the Automatic Tuning Optimizer is called Automatic SQL Tuning.

Under tuning mode, the optimizer can take several minutes to tune a single statement. It is both time and resource intensive to invoke the Automatic Tuning Optimizer every time a query has to be hard-parsed. The Automatic Tuning Optimizer is meant to be used for complex and high-load SQL statements that have non-trivial impact on the entire system. The Automatic Database Diagnostic Monitor (ADDM) proactively identifies high-load SQL statements which are good candidates for Automatic SQL Tuning. See Chapter 6, "Automatic Performance Diagnostics".

12.1.2 Types of Tuning Analysis

Automatic SQL Tuning includes four types of tuning analysis: Statistics Analysis

The query optimizer relies on object statistics to generate execution plans. If these statistics are stale or missing, the optimizer does not have the necessary information it needs and can generate poor execution plans. The Automatic Tuning Optimizer checks each query object for missing or stale statistics, and produces two types of output:

  • Recommendations to gather relevant statistics for objects with stale or no statistics.

    Because optimizer statistics are automatically collected and refreshed, this problem may be encountered only when automatic optimizer statistics collection has been turned off. See "Automatic Statistics Gathering".

  • Auxiliary information in the form of statistics for objects with no statistics, and statistic adjustment factor for objects with stale statistics.

This auxiliary information is stored in an object called a SQL Profile. SQL Profiling

The query optimizer can sometimes produce inaccurate estimates about an attribute of a statement due to lack of information, leading to poor execution plans. Traditionally, users have corrected this problem by manually adding hints to the application code to guide the optimizer into making correct decisions. For packaged applications, changing application code is not an option and the only alternative available is to log a bug with the application vendor and wait for a fix.

Automatic SQL Tuning deals with this problem with its SQL Profiling capability. The Automatic Tuning Optimizer creates a profile of the SQL statement called a SQL Profile, consisting of auxiliary statistics specific to that statement. The query optimizer under normal mode makes estimates about cardinality, selectivity, and cost that can sometimes be off by a significant amount resulting in poor execution plans. SQL Profile addresses this problem by collecting additional information using sampling and partial execution techniques to verify and, if necessary, adjust these estimates.

During SQL Profiling, the Automatic Tuning Optimizer also uses execution history information of the SQL statement to appropriately set optimizer parameter settings, such as changing the OPTIMIZER_MODE initialization parameter setting from ALL_ROWS to FIRST_ROWS for that SQL statement.

The output of this type of analysis is a recommendation to accept the SQL Profile. A SQL Profile, once accepted, is stored persistently in the data dictionary. Note that the SQL Profile is specific to a particular query. If accepted, the optimizer under normal mode uses the information in the SQL Profile in conjunction with regular database statistics when generating an execution plan. The availability of the additional information makes it possible to produce well-tuned plans for corresponding SQL statement without requiring any change to the application code.

The scope of a SQL Profile can be controlled by the CATEGORY profile attribute. This attribute determines which user sessions can apply the profile. You can view the CATEGORY attribute for a SQL Profile in CATEGORY column of the DBA_SQL_PROFILES view. By default, all profiles are created in the DEFAULT category. This means that all user sessions where the SQLTUNE_CATEGORY initialization parameter is set to DEFAULT can use the profile.

By altering the category of a SQL profile, you can determine which sessions are affected by the creation of a profile. For example, by setting the category of a SQL Profile to DEV, only those users sessions where the SQLTUNE_CATEGORY initialization parameter is set to DEV can use the profile. All other sessions do not have access to the SQL Profile and execution plans for SQL statements are not impacted by the SQL profile. This technique enables you to test a SQL Profile in a restricted environment before making it available to other user sessions.

See Also:

Oracle Database Reference for information on the SQLTUNE_CATEGORY initialization parameter

It is important to note that the SQL Profile does not freeze the execution plan of a SQL statement, as done by stored outlines. As tables grow or indexes are created or dropped, the execution plan can change with the same SQL Profile. The information stored in it continues to be relevant even as the data distribution or access path of the corresponding statement change. However, over a long period of time, its content can become outdated and would have to be regenerated. This can be done by running Automatic SQL Tuning again on the same statement to regenerate the SQL Profile.

SQL Profiles apply to the following statement types:

  • SELECT statements

  • UPDATE statements

  • INSERT statements (only with a SELECT clause)

  • DELETE statements

  • CREATE TABLE statements (only with the AS SELECT clause)

  • MERGE statements (the update or insert operations)

A complete set of functions are provided for management of SQL Profiles. See "SQL Profiles". Access Path Analysis

Indexes can tremendously enhance performance of a SQL statement by reducing the need for full table scans on large tables. Effective indexing is a common tuning technique. The Automatic Tuning Optimizer also explores whether a new index can significantly enhance the performance of a query. If such an index is identified, it recommends its creation.

Because the Automatic Tuning Optimizer does not analyze how its index recommendation can affect the entire SQL workload, it also recommends running a the SQLAccess Advisor utility on the SQL statement along with a representative SQL workload. The SQLAccess Advisor looks at the impact of creating an index on the entire SQL workload before making any recommendations. See "Automatic SQL Tuning Features". SQL Structure Analysis

The Automatic Tuning Optimizer identifies common problems with structure of SQL statements than can lead to poor performance. These could be syntactic, semantic, or design problems with the statement. In each of these cases the Automatic Tuning Optimizer makes relevant suggestions to restructure the SQL statements. The alternative suggested is similar, but not equivalent, to the original statement.

For example, the optimizer may suggest to replace UNION operator with UNION ALL or to replace NOT IN with NOT EXISTS. An application developer can then determine if the advice is applicable to their situation or not. For instance, if the schema design is such that there is no possibility of producing duplicates, then the UNION ALL operator is much more efficient than the UNION operator. These changes require a good understanding of the data properties and should be implemented only after careful consideration.

12.2 SQL Tuning Advisor

The Automatic SQL Tuning capabilities are exposed through a server utility called the SQL Tuning Advisor. The SQL Tuning Advisor takes one or more SQL statements as an input and invokes the Automatic Tuning Optimizer to perform SQL tuning on the statements. The output of the SQL Tuning Advisor is in the form of an advice or recommendations, along with a rationale for each recommendation and its expected benefit. The recommendation relates to collection of statistics on objects, creation of new indexes, restructuring of the SQL statement, or creation of SQL Profile. A user can choose to accept the recommendation to complete the tuning of the SQL statements.

The SQL Tuning Advisor input can be a single SQL statement or a set of statements. For tuning multiple statements, a SQL Tuning Set (STS) has to be first created. An STS is a database object that stores SQL statements along with their execution context. An STS can be created manually using command line APIs or automatically using Oracle Enterprise Manager. See "SQL Tuning Sets".

This section cover the following topics related to the SQL Tuning Advisor:

12.2.1 Input Sources

The input for the SQL Tuning Advisor can come from several sources. These input sources include:

  • Automatic Database Diagnostic Monitor

    The primary input source is the Automatic Database Diagnostic Monitor (ADDM). By default, ADDM runs proactively once every hour and analyzes key statistics gathered by the Automatic Workload Repository (AWR) over the last hour to identify any performance problems including high-load SQL statements. If a high-load SQL is identified, ADDM recommends running SQL Tuning Advisor on the SQL. See "Automatic Database Diagnostic Monitor".

  • High-load SQL statements

    The second most important input source is the high-load SQL statements captured in Automatic Workload Repository (AWR). The AWR takes regular snapshots of the system activity including high-load SQL statements ranked by relevant statistics, such as CPU consumption and wait time. A user can view the AWR and identify the high-load SQL of interest and run SQL Tuning Advisor on them. By default, the AWR retains data for the last seven days. This means that any high-load SQL that ran within the retention period of the AWR can be located and tuned using this feature. See "Overview of the Automatic Workload Repository".

  • Cursor cache

    The third likely source of input is the cursor cache. This source is used for tuning recent SQL statements that are yet to be captured in the AWR. The cursor cache and AWR together provide the capability to identify and tune high-load SQL statements from the current time going as far back as the AWR retention allows, which by default is at least 7 days.

  • SQL Tuning Set

    Another possible input source for the SQL Tuning Advisor is the SQL Tuning Set. A SQL Tuning Set (STS) is a database object that stores SQL statements along with their execution context. An STS can include SQL statements that are yet to be deployed, with the goal of measuring their individual performance, or identifying the ones whose performance falls short of expectation. When a set of SQL statements are used as input, a SQL Tuning Set (STS) has to be first constructed and stored. See "SQL Tuning Sets".

12.2.2 Tuning Options

SQL Tuning Advisor provides options to manage the scope and duration of a tuning task. The scope of a tuning task can be set to limited or comprehensive.

  • If the limited option is chosen, the SQL Tuning Advisor produces recommendations based on statistics checks, access path analysis, and SQL structure analysis. SQL Profile recommendations are not generated.

  • If the comprehensive option is selected, the SQL Tuning Advisor carries out all the analysis it performs under limited scope plus SQL Profiling. With the comprehensive option you can also specify a time limit for the tuning task, which by default is 30 minutes.

12.2.3 Advisor Output

After analyzing the SQL statements, the SQL Tuning Advisor provides advice on optimizing the execution plan, the rationale for the proposed optimization, the estimated performance benefit, and the command to implement the advice. You simply have to choose whether or not to accept the recommendations to optimize the SQL statements.

12.2.4 Using SQL Tuning Advisor APIs

The recommended interface for running the SQL Tuning Advisor is the Oracle Enterprise Manager. Whenever possible, you should run the SQL Tuning Advisor using Oracle Enterprise Manager, as described in the Oracle Database 2 Day + Performance Tuning Guide. If Oracle Enterprise Manager is unavailable, you can run the SQL Tuning Advisor using procedures in the DBMS_SQLTUNE package. To use the APIs, the user must be granted specific privileges.

See Also:

Oracle Database PL/SQL Packages and Types Reference for information on the security model for the DBMS_SQLTUNE package

Running SQL Tuning Advisor using DBMS_SQLTUNE package is a multi-step process:

  1. Create a SQL Tuning Set (if tuning multiple SQL statements)

  2. Create a SQL tuning task

  3. Execute a SQL tuning task

  4. Display the results of a SQL tuning task

  5. Implement recommendations as appropriate

A SQL tuning task can be created for a single SQL statement. For tuning multiple statements, a SQL Tuning Set (STS) has to be first created. An STS is a database object that stores SQL statements along with their execution context. An STS can be created manually using command line APIs or automatically using Oracle Enterprise Manager. See "SQL Tuning Sets".

Figure 12-1 shows the steps involved when running the SQL Tuning Advisor using the DBMS_SQLTUNE package.

Figure 12-1 SQL Tuning Advisor APIs

Description of Figure 12-1 follows
Description of "Figure 12-1 SQL Tuning Advisor APIs"

This section covers the following topics:

See Also:

Oracle Database PL/SQL Packages and Types Reference for detailed information on the DBMS_SQLTUNE package Creating a SQL Tuning Task

You can create tuning tasks from the text of a single SQL statement, a SQL Tuning Set containing multiple statements, a SQL statement selected by SQL identifier from the cursor cache, or a SQL statement selected by SQL identifier from the Automatic Workload Repository.

For example, to use the SQL Tuning Advisor to optimize a specified SQL statement text, you need to create a tuning task with the SQL statement passed as a CLOB argument. For the following PL/SQL code, the user HR has been granted the ADVISOR privilege and the function is run as user HR on the employees table in the HR schema.

 my_task_name VARCHAR2(30);
 my_sqltext   CLOB;
 my_sqltext := 'SELECT /*+ ORDERED */ * '                      ||
               'FROM employees e, locations l, departments d ' ||
               'WHERE e.department_id = d.department_id AND '  ||
                     'l.location_id = d.location_id AND '      ||
                     'e.employee_id < :bnd';

         sql_text    => my_sqltext,
         bind_list   => sql_binds(anydata.ConvertNumber(100)),
         user_name   => 'HR',
         scope       => 'COMPREHENSIVE',
         time_limit  => 60,
         task_name   => 'my_sql_tuning_task',
         description => 'Task to tune a query on a specified employee');

In this example, 100 is the value for bind variable :bnd passed as function argument of type SQL_BINDS, HR is the user under which the CREATE_TUNING_TASK function analyzes the SQL statement, the scope is set to COMPREHENSIVE which means that the advisor also performs SQL Profiling analysis, and 60 is the maximum time in seconds that the function can run. In addition, values for task name and description are provided.

The CREATE_TUNING_TASK function returns the task name that you have provided or generates a unique task name. You can use the task name to specify this task when using other APIs. To view the task names associated with a specific owner, you can run the following:

SELECT task_name FROM DBA_ADVISOR_LOG WHERE owner = 'HR'; Executing a SQL Tuning Task

After you have created a tuning task, you need to execute the task and start the tuning process. For example:

  DBMS_SQLTUNE.EXECUTE_TUNING_TASK( task_name => 'my_sql_tuning_task' );
/ Checking the Status of a SQL Tuning Task

You can check the status of the task by reviewing the information in the USER_ADVISOR_TASKS view or check execution progress of the task in the V$SESSION_LONGOPS view. For example:

SELECT status FROM USER_ADVISOR_TASKS WHERE task_name = 'my_sql_tuning_task'; Checking the Progress of the SQL Tuning Advisor

You can check the execution progress of the SQL Tuning Advisor in the V$ADVISOR_PROGRESS view. For example:

SELECT sofar, totalwork FROM V$ADVISOR_PROGRESS WHERE user_name = 'HR' AND task_name = 'my_sql_tuning_task';

See Also:

Oracle Database Reference for information on the V$ADVISOR_PROGRESS view Displaying the Results of a SQL Tuning Task

After a task has been executed, you display a report of the results with the REPORT_TUNING_TASK function. For example:


The report contains all the findings and recommendations of Automatic SQL Tuning. For each proposed recommendation, the rationale and benefit is provided along with the SQL commands needed to implement the recommendation.

Additional information about tuning tasks and results can be found in DBA views. See "SQL Tuning Information Views". Additional Operations on a SQL Tuning Task

You can use the following APIs for managing SQL tuning tasks:

  • INTERRUPT_TUNING_TASK to interrupt a task while executing, causing a normal exit with intermediate results

  • RESUME_TUNING_TASK to resume a previously interrupted task

  • CANCEL_TUNING_TASK to cancel a task while executing, removing all results from the task

  • RESET_TUNING_TASK to reset a task while executing, removing all results from the task and returning the task to its initial state

  • DROP_TUNING_TASK to drop a task, removing all results associated with the task

12.3 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)

SQL statements can be filtered using the application module name and action, or any of the execution statistics. In addition, the SQL statements can be ranked based on any combination of execution statistics.

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. When poorly performing SQL statements are encountered on a production system, it may not be desirable for developers to perform their investigation and tuning activities on the production system directly. This feature allows the DBA to transport the offending SQL statements to a test system where the developers can safely analyze and tune them. To transport SQL Tuning Sets, use the DBMS_SQLTUNE package procedures.

The recommended interface for managing SQL tuning sets is the Oracle Enterprise Manager. Whenever possible, you should manage SQL tuning sets using Oracle Enterprise Manager, as described in the Oracle Database 2 Day + Performance Tuning Guide. If Oracle Enterprise Manager is unavailable, you can manage SQL tuning sets using the DBMS_SQLTUNE package procedures. Typically you would use the STS operations in the following sequence:

  • Create a new STS

  • Load the STS

  • Select the STS to review the contents

  • Update the STS if necessary

  • Create a tuning task with the STS as input

  • Transporting the STS to another system if necessary

  • Drop the STS when finished

To use the APIs, you need the ADMINISTER SQL TUNING SET system privilege to manage SQL Tuning Sets that you own, or the ADMINISTER ANY SQL TUNING SET system privilege to manage any SQL Tuning Sets.

Figure 12-2 shows the steps involved when using SQL Tuning Sets APIs.

Figure 12-2 SQL Tuning Sets APIs

Description of Figure 12-2 follows
Description of "Figure 12-2 SQL Tuning Sets APIs"

This section covers the following topics:

See Also:

Oracle Database PL/SQL Packages and Types Reference for detailed information on the DBMS_SQLTUNE package

12.3.1 Creating a SQL Tuning Set

The CREATE_SQLSET procedure is used to create an empty STS object in the database. For example, the following procedure creates an STS object that could be used to tune I/O intensive SQL statements during a specific period of time:

    sqlset_name => 'my_sql_tuning_set', 
    description  => 'I/O intensive workload');

where my_sql_tuning_set is the name of the STS in the database and 'I/O intensive workload' is the description assigned to the STS.

12.3.2 Loading a SQL Tuning Set

The LOAD_SQLSET procedure populates the STS with selected SQL statements. The standard sources for populating an STS are the workload repository, another STS, or the cursor cache. For both the workload repository and STS, there are predefined table functions that can be used to select columns from the source to populate a new STS.

In the following example, procedure calls are used to load my_sql_tuning_set from an AWR baseline called peak baseline. The data has been filtered to select only the top 30 SQL statements ordered by elapsed time. First a ref cursor is opened to select from the specified baseline. Next the statements and their statistics are loaded from the baseline into the STS.

 OPEN baseline_cursor FOR
                  'peak baseline',
                   NULL, NULL,
                   NULL, NULL, NULL,
                   30)) p;

             sqlset_name     => 'my_sql_tuning_set',
             populate_cursor => baseline_cursor);

12.3.3 Displaying the Contents of a SQL Tuning Set

The SELECT_SQLSET table function reads the contents of the STS. After an STS has been created and populated, you can browse the SQL in the STS using different filtering criteria. The SELECT_SQLSET procedure is provided for this purpose.

In the following example, the SQL statements in the STS are displayed for statements with a disk-reads to buffer-gets ratio greater than or equal to 75%.

   '(disk_reads/buffer_gets) >= 0.75'));

Additional details of the SQL Tuning Sets that have been created and loaded can also be displayed with DBA views, such as DBA_SQLSET, DBA_SQLSET_STATEMENTS, and DBA_SQLSET_BINDS.

12.3.4 Modifying a SQL Tuning Set

SQL statements can be updated and deleted from a SQL Tuning Set based on a search condition. In the following example, the DELETE_SQLSET procedure deletes SQL statements from my_sql_tuning_set that have been executed less than fifty times.

      sqlset_name  => 'my_sql_tuning_set',
      basic_filter => 'executions < 50');

12.3.5 Transporting a SQL Tuning Set

SQL Tuning Sets can be transported to another system by first exporting the STS from one system to a staging table, then importing the STS from the staging table into another system.

To transport a SQL Tuning Set:

  1. Use the CREATE_STGTAB_SQLSET procedure to create a staging table where the SQL Tuning Sets will be exported.

    The following example shows how to create a staging table named staging_table.

      DBMS_SQLTUNE.CREATE_STGTAB_SQLSET( table_name => 'staging_table' );
  2. Use the PACK_STGTAB_SQLSET procedure to export SQL Tuning Sets into the staging table.

    The following example shows how to export a SQL Tuning Set named my_sts to the staging table.

          sqlset_name  => 'my_sts',
          staging_table_name => 'staging_table');
  3. Move the staging table to the system where the SQL Tuning Sets will be imported using the mechanism of choice (such as datapump or database link).

  4. On the system where the SQL Tuning Sets will be imported, use the UNPACK_STGTAB_SQLSET procedure to import SQL Tuning Sets from the staging table.

    The following example shows how to import SQL Tuning Sets contained in the staging table.

          sqlset_name  => '%',
          replace  => TRUE,
          staging_table_name => 'staging_table');

12.3.6 Dropping a SQL Tuning Set

The DROP_SQLSET procedure is used to drop an STS that is no longer needed. For example:

  DBMS_SQLTUNE.DROP_SQLSET( sqlset_name => 'my_sql_tuning_set' );

12.3.7 Additional Operations on SQL Tuning Sets

You can use the following APIs to manage an STS:

  • Updating the attributes of SQL statements in an STS

    The UPDATE_SQLSET procedure updates the attributes of SQL statements (such as PRIORITY or OTHER) in an existing STS identified by STS name and SQL identifier.

  • Capturing the full system workload

    The CAPTURE_CURSOR_CACHE_SQLSET function enables the capture of the full system workload by repeatedly polling the cursor cache over a specified interval. This function is a lot more efficient than repeatedly using the SELECT_CURSOR_CACHE and LOAD_SQLSET procedures to capture the cursor cache over an extended period of time. This function effectively captures the entire workload, as opposed to the AWR—which only captures the workload of high-load SQL statements—or the LOAD_SQLSET procedure, which accesses the data source only once.

  • Adding and removing a reference to an STS

    The ADD_SQLSET_REFERENCE function adds a new reference to an existing STS to indicate its use by a client. The function returns the identifier of the added reference. The REMOVE_SQLSET_REFERENCE procedure is used to deactivate an STS to indicate it is no longer used by the client.

12.4 SQL Profiles

While SQL Profiles are usually handled by Oracle Enterprise Manager as part of the Automatic SQL Tuning process, SQL Profiles can be managed through the DBMS_SQLTUNE package. To use the SQL Profiles APIs, you need the CREATE ANY SQL_PROFILE, DROP ANY SQL_PROFILE, and ALTER ANY SQL_PROFILE system privileges.

Figure 12-3 shows the steps involved when using SQL Profiles APIs.

Figure 12-3 SQL Profiles APIs

Description of Figure 12-3 follows
Description of "Figure 12-3 SQL Profiles APIs"

This section covers the following topics:

See Also:

Oracle Database PL/SQL Packages and Types Reference for detailed information on the DBMS_SQLTUNE package

12.4.1 Accepting a SQL Profile

When the SQL Tuning Advisor recommends that a SQL Profile be used, you should accept the SQL Profile that is recommended. In cases where the SQL Tuning Advisor recommends that an index and a SQL Profile be used, both should be used. You can use the DBMS_SQLTUNE.ACCEPT_SQL_PROFILE procedure to accept a SQL Profile recommended by the SQL Tuning Advisor. This creates and stores a SQL Profile in the database. For example:

 my_sqlprofile_name VARCHAR2(30);
 my_sqlprofile_name := DBMS_SQLTUNE.ACCEPT_SQL_PROFILE ( 
    task_name    => 'my_sql_tuning_task',
    name         => 'my_sql_profile',)
    force_match  => TRUE);

In this example, my_sql_tuning_task is the name of the SQL tuning task and my_sql_profile is the name of the SQL Profile that you want to accept.

Typically, an accepted SQL Profile is associated with the SQL statement through a special SQL signature that is generated using a hash function. This hash function normalizes the SQL statement for case (changes the entire SQL statement to upper case) and white spaces (removes all extra whites spaces) before generating the signature. The same SQL Profile thus will work for all SQL statements that are essentially the same, where the only difference is in case usage and white spaces. However, by setting force_match to true, the SQL Profile will additionally target all SQL statements that have the same text after normalizing literal values to bind variables. This may be useful for applications that use literal values rather than bind variables, since this will allow SQL with text differing only in its literal values to share a SQL Profile. If both literal values and bind variables are used in the SQL text, or if this parameter is set to false (the default value), literal values will not be normalized.

You can view information about a SQL Profile in the DBA_SQL_PROFILES view.

12.4.2 Altering a SQL Profile

You can alter the STATUS, NAME, DESCRIPTION, CATEGORY and FORCE_MATCH attributes of an existing SQL Profile with the ALTER_SQL_PROFILE procedure. For example:

     name            => 'my_sql_profile', 
     attribute_name  => 'STATUS', 
     value           => 'DISABLED');

In this example, my_sql_profile is the name of the SQL Profile that you want to alter. The status attribute is changed to disabled which means the SQL Profile is not used during SQL compilation.

12.4.3 Dropping a SQL Profile

You can drop a SQL Profile with the DROP_SQL_PROFILE procedure. For example:

  DBMS_SQLTUNE.DROP_SQL_PROFILE(name => 'my_sql_profile');

In this example, my_sql_profile is the name of the SQL Profile you want to drop. You can also specify whether to ignore errors raised if the name does not exist. For this example, the default value of FALSE is accepted.

12.5 SQL Tuning Information Views

This section summarizes the views that you can display to review information that has been gathered for tuning the SQL statements. You need DBA privileges to access these views.


  • SQL tuning information views, such as DBA_SQLTUNE_STATISTICS, DBA_SQLTUNE_BINDS, and DBA_SQLTUNE_PLANS views.


  • Information on captured execution plans for statements in SQL Tuning Sets are displayed in the DBA_SQLSET_PLANS and USER_SQLSET_PLANS views.

  • SQL Profile information is displayed in the DBA_SQL_PROFILES view.

  • Advisor execution progress information is displayed in the V$ADVISOR_PROGRESS view.

  • Dynamic views containing information relevant to the SQL tuning, such as V$SQL, V$SQLAREA, V$SQLSTATS, and V$SQL_BINDS views.

    See Also:

    Oracle Database Reference for information on static data dictionary and dynamic views