getting started with tuning sql statements in ibm data

Getting Started with Tuning SQL Statements in IBM Data Studio and IBM Data Studio (stand-alone), Version 2.2.1

Note Before using this information and the product it supports, read the information in “Notices” on page 63.
Contents
Configuring a DB2 for z/OS subsystem for query tuning . . . . . . . . . . . 11
Setting global preferences . . . . . . 25
Tuning SQL statements . . . . . . . 43
Additional resources. . . . . . . . . 61
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iv Getting Started with Tuning SQL Statements in IBM Data Studio and IBM Data Studio (stand-alone), Version 2.2.1
Introduction
This document explains the basics of using IBM® Data Studio and IBM Data Studio (stand-alone), Version 2.2.1 for tuning SQL statements.
Note: For simplicity, this guide refers to both IBM Data Studio and IBM Data Studio (stand-alone) as IBM Data Studio, except in the section that is specific to installing IBM Data Studio (stand-alone).
To help you get started with tuning, this document shows you how to complete these tasks: 1. Install IBM Data Studio (stand-alone). 2. Configure a DB2® for z/OS® subsystem, so that you can tune SQL statements
that run on that subsystem. 3. (Optional) Set global preferences for tuning. 4. Select an SQL statement to tune. 5. Run the Statistics Advisor and analysis tools, and generate reports. 6. Capture the runtime environment of an SQL statement.
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2 Getting Started with Tuning SQL Statements in IBM Data Studio and IBM Data Studio (stand-alone), Version 2.2.1
Installing IBM Data Studio (stand-alone), Version 2.2.1
This chapter explains how to download the IBM Data Studio (stand-alone) product and install it. The procedure involves ensuring that your system meets the requirements, downloading and extracting the product package, and then running an installation wizard.
Here are the steps: 1. Ensure that your Linux® or Windows® system meets the requirements that are
documented here: http://www-01.ibm.com/support/docview.wss?rs=3360 &uid=swg27016061
2. Download IBM Data Studio (stand-alone), Version 2.2.1 from this location. You will need an IBM ID and password, which you can create at this location if you do not already an account. https://www14.software.ibm.com/webapp/ iwm/web/preLogin.do?lang=en_US&source=swg-idssa
3. Extract the product package to a temporary directory on your computer, such as c:\temp.
4. (Optional) The product installation program requires a JRE at level 1.6 or higher. To use the JRE that is bundled with the product, configure the JAVA_HOME and PATH environment variables as follows, replacing temp with the path and name of the directory where you extracted the product.
On Windows set JAVA_HOME=C:\temp\datastudio\eclipse\jreset PATH=C:\temp\ datastudio\eclipse\jre\bin;%PATH%
On Linux export JAVA_HOME=/root/temp/datastudio/eclipse/jre export PATH=/root/temp/datastudio/eclipse/jre/bin:$PATH
5. From the directory where you extracted the product, run the executable file.
Figure 1. The extracted product package in a temporary directory
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On Windows On Windows, run install.exe.
On Linux On Linux, run ./install.bin.
6. In the wizard, select the language that you want the installation wizard to use and click OK.
7. On the Introduction page, click Next. The Next button always appears in the bottom-right corner of the wizard.
Figure 2. The splash screen for the installation wizard, where you can select a language
8. On the Software License Agreement page, read and accept the license agreement. Then, click Next.
Figure 3. The Introduction page
Installing IBM Data Studio (stand-alone), Version 2.2.1 5
9. On the Choose Install Folder page, select a directory for the installation. If you do not accept the default directory, ensure that you do not choose a directory that has a path that is long, deep, or both. An example of a long path on Microsoft Windows is c:\ this_is_the_directory_where_I_want_to_install_IBM_Data_Studio_standalone. An example of a deep path is c:\this\is\an\example\of\a\deep\path. If the directory that you choose has a path that meets either or both of these criteria, you might encounter problems when you are using the product. After selecting the directory, click Next.
Figure 4. The software license agreement
10. On the Pre-Installation Summary page, click Install in the bottom-right corner.
Figure 5. The Choose Install Folder page
11. When the installation is finished, click Done in the bottom-right corner to start IBM Data Studio (stand-alone).
Figure 6. The Pre-Installation Summary page
At other times when you want to use the product, in Windows you can click Start and select Programs > IBM Data Studio Standalone > IBM Data Studio 2.2.
Figure 7. The final page of the installation wizard
Configuring a DB2 for z/OS subsystem for query tuning
Configuring a DB2 for z/OS subsystem for query tuning involves these tasks. v Binding packages that the Statistics Advisor and other features require, and
grant privileges on those packages v Creating a set of EXPLAIN tables, if your subsystem does not have a set of them
already, and grant privileges on them v Creating a set of Query Tuner tables
You can complete these tasks by following these steps: 1. Define a database connection profile, connect to a DB2 for z/OS subsystem,
and set the default SQL ID and schema. 2. Follow either of these procedures to configure the DB2 for z/OS subsystem for
query tuning: v Configure the subsystem by using the Configure Subsystem for SQL Tuning
wizard v Configure the subsystem by running JCL
Defining a database connection profile, connecting to a DB2 for z/OS subsystem, and setting the default SQL ID and schema 1. In the Data Source Explorer, right-click Database connections and select New.
2. In the New Connection wizard, complete these steps, using this image for reference:
Figure 8. Creating a new connection in the Data Source Explorer
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a. Under Select a database manager, select DB2 for z/OS. b. To the right in the Properties box, specify the location of the subsystem, the
name of the host where the subsystem is located, and the port number to use when connecting to the host.
c. Deselect the Use default naming convention check box and specify a new name for the connection, if you do not want to use the location as the default name.
d. Specify the user name (authorization ID) and password to use for connections to the subsystem.
e. Click the Test Connection button. f. Click Finish if the test of the connection was successful. When you click
Finish, the Data Source Explorer shows that a connection to the subsystem is open. From this point on, whenever you want to open a connection to the subsystem, right-click the connection profile and select Connect.
3. Set the default SQL ID and schema to use for configuring the subsystem by using Data Studio and for tuning SQL statements a. In the Data Source Explorer, right-click the subsystem and select Query
Tuner > Change Default SQL ID and Schema.
Figure 9. The New Connection wizard
b. Edit the values. The SQL ID is always folded to uppercase. You cannot use quotation marks to preserve mixed case or lowercase. The case in which you type the schema is preserved, however. If you type sChEmA, the default schema is sChEmA.
c. Click OK.
Configure the subsystem by using the Configure Subsystem for SQL Tuning wizard
Before completing these steps, ensure that you have the necessary authorities and privileges, which are listed here in the Data Studio information center. 1. Ensure that you have the required authorities and privileges.
Table 1. Authorities and privileges required to connect to and configure a DB2 for z/OS subsystem for tuning, when configuring from IBM Data Studio
Task Authorities or privileges required
Connect to a DB2 for z/OS subsystem All of the following authorities and privileges: v Underlying DB2 access authority v EXECUTE privilege on the following
packages:
basic packages (DSN5OADM, DSN5OEPJ (DB2 for z/OS Version 8), DSN5OEPK (DB2 for z/OS Versions 9 and 10), DSN5ONPT, DSN5OPKG)
Figure 10. Right-clicking the subsystem in the Data Source Explorer and opening the Change Default SQL ID and Schema window
Configuring a DB2 for z/OS subsystem for query tuning 13
Bind packages One of the following authorities and privileges: v SYSADM or DBADM authority v BINDADD privilege if required packages
do not exist, and CREATEIN privilege on the schema
v ALTERIN privilege on the schema if the required packages exist
v BIND privilege on the required packages if they exist
Free packages One of the following authorities and privileges: v Ownership of the packages v BINDAGENT privilege that is granted by
the owner of the packages v SYSCTRL authority v SYSADM authority v PACKADM authority for the collection or
for all collections
Browse subsystem parameters All of the following authorities and privileges:
v EXECUTE privilege on the SYSPROC.DSNWZP stored procedure
v At least MONITOR1 system privilege
Manage users One of the following privileges or authorities: v The privilege WITH GRANT OPTION on
required packages v Ownership of the packages v SYSADM authority
Table 2. Authorities and privileges required to enable the EXPLAIN function on a DB2 for z/OS subsystem, when configuring from IBM Data Studio
Create EXPLAIN tables If you want to create the EXPLAIN tables in a new database, one or more of the following privileges or authorities for creating the database: v CREATEDBA privilege v CREATEDBC privilege v SYSADM or SYSCTRL authority
For creating the table space, one or more of the following privileges or authorities: v CREATETS privilege for the database v DBADM, DBCTRL, or DBMAINT
authority for the database v SYSADM or SYSCTRL authority
For creating the tables, one or more of the following privileges or authorities: v CREATETAB privilege for the database v DBADM, DBCTRL, or DBMAINT
authority for the database v SYSADM or SYSCTRL authority
Create aliases for existing EXPLAIN tables One of the following privileges or authorities: v The CREATEALIAS privilege v SYSADM or SYSCTRL authority v DBADM or DBCTRL authority on the
database that contains the table, if the alias is for a table and the value of field DBADM CREATE AUTH on installation panel DSNTIPP is YES
2. In the Data Source Explorer, right-click the subsystem and select Query Tuner > Configure for Tuning > Guided Configuration. The Configure Subsystem for SQL Tuning wizard opens.
The first page lists all of the steps for configuring the subsystem. You complete these steps on the subsequent pages of the wizard. Click Next to go to the first step.
3. On the Bind Packages page, specify the package owner for all the Query Tuner packages, which the Statistics Advisor and other tuning features require. If other users are going to be tuning SQL statements that run on this subsystem, select the check box Grant or revoke authorization on packages. You can grant authorizations to those other users on a subsequent page of the wizard.
Figure 11. The Introduction page
When you are finished on this page, click Next. 4. On the Create EXPLAIN Tables page, specify the SQL ID that is authorized to
create the EXPLAIN tables. You can change the qualifier for the EXPLAIN tables by clicking the Select button. Specify unique names for the LOB table spaces to be created and, if necessary, edit the parameters for allocating the table spaces. The buffer pools and storage groups must already exist. They are not allocated automatically. Everyone who tunes SQL statements must be authorized to select from, insert into, and update the EXPLAIN tables. If you know of people who need these authorities, select the check box Grant or revoke authorizations on EXPLAIN tables. If you want to share the EXPLAIN tables under an alias, select the check box Create aliases for EXPLAIN tables.
Figure 12. The Bind Packages page
When you are finished on this page, click Next. 5. On the Create Query Tuner Tables page, specify the storage group and buffer
pool in which to create tables that the Statistics Advisor accesses. Then, click Next.
Figure 13. The Create EXPLAIN Tables page
6. If you selected the Grant or revoke authorization on packages check box on the Bind Packages page, the Grant Privileges on Query Tuner Packages page appears next. Grant privileges to each authorization ID that will be used for tuning SQL statements. Then, click Next.
Note: Because you are using IBM Data Studio (stand-alone), ignore the warning that appears at the bottom of the page.
Figure 14. The Create Query Tuner Tables page
7. If you selected the Grant or revoke authorizations on EXPLAIN tables check box on the Create EXPLAIN Tables page, the Grant Privileges on EXPLAIN Tables page opens next. Specify the SQL ID that is authorized to grant these privileges. Specify the qualifier of the set of EXPLAIN tables that you want to grant privileges on. Then, grant privileges to each authorization ID that will be used for tuning SQL statements. When you are finished on this page, click Next.
Figure 15. The Grant Privileges on Query Tuner Packages page
8. If you selected the Create aliases for EXPLAIN tables check box on the Create EXPLAIN Tables page, the Create Aliases for EXPLAIN Tables page opens. Create an alias for each authorization ID that will have access to the EXPLAIN tables. You can enter multiple aliases with a comma separator. When you are finished on this page, click Next.
Figure 16. The Grant Privileges on EXPLAIN Tables page
9. On the Summary page, review the list of tasks that you specified. You can click Back to return to previous pages in the wizard and change values. When you are finished reviewing the tasks, click Finish. The wizard attempts to complete each task in the list.
Figure 17. The Create Aliases for EXPLAIN Tables page
Configuring the subsystem by running JCL
Perform the following steps on the DB2 for z/OS subsystem to configure it for tuning SQL statements: 1. Upload the required DBRM and JCL job files to the subsystem. The files are
installed with Data Studio. You can find these files in the following location: Installation_directory\ dsrcp\ZOS\z/OS_version_number_and_mode
Figure 18. The Summary page
Note: Use binary format when you upload these DBRM files to the subsystem. 2. Modify the corresponding AOCDDL JCL job file in the following table to
conform to your environment, and submit the job to install the DBRM files and create EXPLAIN tables.
Subsystem JCL job file
DB2 Version 10 for z/OS conversion mode from Version 9
AOCDDLX9
DB2 Version 10 for z/OS conversion mode from Version 8
AOCDDLX8
DB2 for z/OS Version 8 new-function mode AOCDDL8N
DB2 for z/OS Version 8 compatibility mode AOCDDL8C
Setting global preferences
Every time that you run the Statistics Advisor and analysis tools, or generate reports, you can set values for preferences that modify how these features work. However, you can also set default values for these preferences ahead of time in the Preferences window.
Important: If you set default values for these preferences while one or more instances of workflow assistant are open, you must close those instances and then reopen them for the default values to take effect.
To open the Preferences window, in the menubar at the top of IBM Data Studio click Window. Then, select Preferences.
In the Preferences window, expand Data Management and select Query Tuner. The parent page for the tuning preferences opens. All of the preferences on this page are applicable to tuning in IBM Data Studio, except for the Check user privileges before monitoring or scheduling snapshots for Monitor Profiles preference.
Figure 19. Opening the Preferences window
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For help with the preferences about the trace settings and migrating EXPLAIN
tables, refer to their tooltips. For help with the other preferences, click the icon in the lower-left corner of the Preferences window.
Of the pages under the Query Tuner page, only those that are highlighted in yellow in this image are applicable to IBM Data Studio.
Figure 20. The Query Tuner page
On the EXPLAIN Query page of the preferences, you can set options that are related to collecting EXPLAIN information about the SQL statements that you want to tune. For help with these preferences, refer to their tooltips.
Select the Always refresh catalog information from the data server check box so that the local cache of the catalog is updated before EXPLAIN information is collected for SQL statements. The Statistics Advisor, access plan graphs, and access plan reports depend on current EXPLAIN information. When you start the EXPLAIN process for an SQL statement that you want to tune, the process uses catalog information that is locally cached. If the SQL statement references any tables that change after you explain that statement for the first time, you should refresh the local cache of the catalog before you explain the statement again. You can refresh the cache automatically by selecting this check box. If you do not select it, you can refresh the cache manually before you run the Statistics Advisor and tools on the statement. In the Data Source Explorer, right-click the subsystem and select Query Tuner > Refresh Catalog for Tuning.
The preference Use the stored procedure to execute EXPLAIN for the statement cache refers to the DB2 for z/OS dynamic statement cache, from which you can
Figure 21. Preference pages that are applicable to IBM Data Studio
Setting global preferences 27
capture SQL statements to tune.
On the Access Plan Report page, you can specify which reports to generate and their formats.
Figure 22. The EXPLAIN Query page
On the Statistics Advisor page, choose defaults for the Statistics Advisor to use when generating RUNSTATS commands to recommend. Select the Custom option to set a default value for each preference. For help with the preferences, refer to
tooltips and click the icon in the lower-left corner of the Preferences window.
Figure 23. The Access Plan Report page
Figure 24. The general preferences for the Statistics Advisor
Figure 25. The first set of preferences for the Statistics Advisor for DB2 for z/OS
Figure 26. The second set of preferences for the Statistics Advisor for DB2 for z/OS
Selecting an SQL statement to tune
Now that the subsystem is set up to support tuning SQL statements, you can select an SQL statement to tune.
There are many locations from which you can choose an SQL statement to tune. You can access most of those locations from within the workflow assistant, which is the part of the Data Studio interface where the tuning features are collected together. You will learn more about choosing an SQL statement while you are in the workflow assistant shortly.
Selecting an SQL statement from outside of the workflow assistant
First, here is a list of locations outside of the workflow assistant in which you can select an SQL statement to tune.
SQL editor and routine editor Place the cursor on an SQL statement, right-click, and select Start Tuning.
You can also right-click anywhere in one of these editors and select Start Tuning.
View, SQL stored procedure, user-defined function, or trigger in the Data Source Explorer
Right-click any of these objects and select Query Tuner > Start Tuning.
Figure 27. Right-clicking a view in the Data Source Explorer
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If you select Start Tuning after right-clicking on a view, a SELECT statement is reverse engineered from the view. The workflow assistant then opens so that you can tune this statement.
If you select Start Tuning from any of the other locations, this is how the workflow assistant responds: v If the object contains one SQL statement, the workflow assistant opens so that
you can tune the statement. v If the object contains more than one SQL statement, the workflow assistant
allows you to select one of the statements to tune.
Selecting an SQL statement from inside the workflow assistant
Open the workflow assistant from the Data Source Explorer in either of two ways. v Right-click the database connection and select Start Tuning.
v Expand the database connection, right-click the subsystem, and select Query Tuner > Start Tuning.
Figure 28. Right-clicking the database connection and selecting Start Tuning
The workflow assistant opens to the Capture SQL from File page of the Capture section.
Figure 29. Right-clicking the subsystem and selecting Query Tuner > Start Tuning
Figure 30. The Capture SQL from File page of the Capture section of the workflow assistant
Selecting an SQL statement to tune 35
The left side of the Capture section lists the different locations that you can capture SQL statements from.
The goal of capturing SQL statements is to bring SQL statements into the workflow assistant and then to sort them to find statements that require tuning. For an example of capturing SQL statements from one of the sources in DB2 for z/OS, click Statement Cache. The Capture SQL from Statement Cache page opens.
The dynamic statement cache, as well as any other source in DB2 for z/OS, can contain a very large number of SQL statements. Therefore, the first step in capturing is to define a filter in which you specify criteria that the statements that you want to examine must match. In the Filter section, click the Create Filter icon.
Figure 31. Locations that you can capture SQL statements from
Figure 32. The Capture SQL from Statement Cache page
When you create a filter for capturing from the dynamic statement cache, you name it and specify the maximum number of SQL statements that you want the filter to capture. For this example, leave the name as Default_1.
The filter runs against the DSN_STATEMENT_CACHE_TABLE table, so you must specify the qualifier for that table. For this example, ignore the two check boxes.
You set the criteria for the filter in the table. SQL statements that the filter captures must match every criterion that you set a value for in this table.
In the next page of the wizard, select the columns that you want the captured statements to be sorted by when the workflow assistant presents them. They will appear in a table in the Capture SQL from Statement Cache page.
Figure 33. The Create Filter icon
Figure 34. The Filter Rows page of the wizard for creating a filter for capturing SQL from the dynamic statement cache
On the Customize Columns page, select the columns that you want to display in the table that lists the captures SQL statements.
Figure 35. The Sort Rows page of the wizard for creating a filter for capturing SQL from the dynamic statement cache
After you click Finish in the wizard, you return to the Capture SQL from Statement Cache page. The filter that you created appears as the selected filter in the Filter name field.
Optional: When you capture SQL statements from the dynamic statement cache, you can also capture runtime metrics for those statements. If you capture those metrics, you can sort on them and more easily identify statements that need tuning than if you captured the SQL statements alone. Click the Enable Cache Trace button to ensure that the metrics are included in the statement cache. Select the Disable cache trace after capturing check box, so that runtime metrics are not cached unnecessarily after you have captured statements. Then, wait while the statements are run and added to the statement cache. When you are sure that the statements of interest to you are cached, you can capture those statements.
Figure 36. The Customize Columns page of the wizard for creating a filter for capturing SQL from the dynamic statement cache
Figure 37. The new filter in the Filter name field
Click Capture. After a few moments, the SQL statements that match the filter criteria appear in a new section: Captured Statements.
If you set any sort columns in the filter wizard, the statements are sorted accordingly. For example, if you chose to sort by the STAT_CPU column in descending order, the statements with the highest CPU cost are at the top of the table. You can also click column headers to sort by individual columns.
If you know that you want to tune a statement that, for example, references a particular table, click the Search for SQL Text icon. In the Find SQL Text window, type the name of the table and click Find Next until you find the right statement.
Figure 38. The Captured Statements section and table of captured SQL statements
After you locate a statement that you want to tune, right-click it and select Invoke Advisors and Tools. You can also click on the statement and then click the Invoke Advisors and Tools icon.
When you capture SQL statements from other sources in DB2 for z/OS, you follow the same steps: 1. Create a filter or use an existing one. You can also edit an existing filter. 2. Click Capture. 3. Look in the table in the Captured Statements section for a statement to tune. 4. Select the statement and click the Invoke Advisors and Tools icon or right-click
the statement and select the Invoke Advisors and Tools option.
The workflow assistant opens to the Run Single-Query Advisors and Analysis Tools page of the Review section. The next chapter explains what to do there.
Figure 39. The Find SQL Text window
Figure 40. The Invoke Advisors and Tools icon and menu option
Tuning SQL statements
After you select the Invoke Advisors and Tools option for an SQL statement, the workflow assistant opens the Run All Single-Query Advisors and Analysis Tools page in the Review section.
The statement appears in the Query Text field at the bottom of the page. The name that the workflow assistant assigns to the statement is in the title of the Query Text field. In the image below, the name of the statement is Query 3.
From this page, you can run the Statistics Advisor, format the statement so that you can read it easily, and generate a graph of the access plan for the statement.
If you want to modify any of the options for the Statistics Advisor, select Set Advisor Options in the top-left corner of the workflow assistant. The options that appear are the same options that appear in the global preferences. If you modify the values for the options here, you override the values that are set in the global preferences. The values will be in effect only for the current instance of the workflow assistant. If you run the Statistics Advisor and then save the recommendations to a project, the values are stored in that project.
Figure 41. The SQL statement in the Query Text field
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After you finish modifying options, select Run All Advisors and Analysis Tools in the top-left corner of the workflow assistant to return to the page where the SQL statement is located.
The first time that you run the Statistics Advisor and analysis tools on a statement, the workflow assistant gathers EXPLAIN information for the statement, if EXPLAIN information is not already available for the statement. You can set values to use for special registers, or you can accept the default values. If EXPLAIN information already exists for the statement, but you modified the objects that the statement references or modified the statement in some way since EXPLAIN information was last collected for it, you can specify to recollect EXPLAIN information.
To the left of the special registers are the SQL ID that has authority to run the statement and the default schema for objects in the statement. If you set the SQL ID and schema in the Change Default SQL ID and Schema window, the values that you specified appear in these fields. However, if you did not set the default SQL ID and schema in that window, these values are used: v If you did not set a default SQL ID, the authorization ID that you are using to
connect to the subsystem is used. v If you did not set a default schema and the objects that are referenced by the
SQL statement are unqualified, the current authorization ID is used. v If you did not set a default schema and the objects that are referenced by the
SQL statement are qualified, the schema from the SQL statement is used.
Figure 42. Setting options locally for the Statistics Advisor
With a check box below these values, you can also specify whether to convert them to uppercase or keep them exactly as you typed them.
When you are ready to run the Statistics Advisor and Analysis Tools, click the Select What To Run button.
The Select Query-Tuning Activities window appears.
Figure 43. Options for the EXPLAIN command, SQL ID, default schema, and the Select What To Run button
Tuning SQL statements 45
For this example, keep the current selection and click OK.
After a few moments, the workflow assistant opens the Review Single-Query Advisor Recommendations page of the Review section.
Figure 44. The Select Query-Tuning Activities window
This page shows that the Statistics Advisor has recommendations. However, before looking at them, select Open Formatted Query in the top-left corner of the workflow assistant. The Review Formatted Query page appears. It shows two versions of the SQL statement: the original statement and the statement as it was revised by the DB2 optimizer. You can save or print the statement.
Figure 45. The Review Single-Query Advisor Recommendations page of the Review section
In the top-left corner of the workflow assistant, select Open Access Plan Graph. The Review Access Plan page displays the graph of the access plan for the statement.
Figure 46. The Review Formatted Query page of the Review section
On the left, click Overview of Diagram for tools for navigating to different areas of a large access plan.
In the diagram, select a node and click Description of Selected Node on the left to see the attributes of that node.
Return to the Review Single-Query Advisor Recommendations by selecting Open Single-Query Recommendations in the top-left corner of the workflow assistant. Then, double-click the row for the Statistics Advisor. The section Statistics Advisor Details opens to show the RUNSTATS commands that the advisor recommends. You can run those commands directly from this section or save them to a file to run them later.
Figure 47. The Review Access Plan page of the Review section
To see the problems that the advisor found with the statistics, expand the section Statistics Advisor report, which is just under the recommended RUNSTATS commands. Expand the section Conflicts detail to learn more about any conflicting statistics that the advisor found. Expand the RUNSTATS Result section if you run the recommended RUNSTATS commands here and want to see whether the commands ran successfully.
Figure 48. The Statistics Advisor Details section
Finally, you can generate two different types of reports to help you decide how to tune the SQL statement.
Summary report In the top-left corner of the workflow assistant, click Open Summary Report. The workflow assistant generates a report that includes this information: v The RUNSTATS commands that are recommended by the Statistics
Advisor v Information about the access plan for the SQL statement v Catalog information about the tables that the statement references and
the indexes that are on those tables
You can save the report to a file. You can also right-click the node and select Print to print the report.
Figure 49. The Statistics Advisor report, Conflicts detail, and RUNSTATS Result sections
Access path reports In the top-left corner of the workflow assistant, click Open Access Path Reports. The workflow assistant opens a window for you to select which reports to generate. You can generate three reports that contain information that the DB2 optimizer uses when generating an access plan for the statement. v A report that contains information about the tables that the statement
references v A report about the predicates that are in the statement v A report about the indexes that are on the tables that the statement
references
After you run the RUNSTATS commands that the Statistics Advisor recommends, you can regenerate the access plan graph of the SQL statement to see how the access plan has changed. If any changes occur, however, to the objects that the SQL statement references, you must refresh the local cache of the system catalog. Then, re-run the Statistics Advisor to find out whether there are any new recommendations. To refresh the local cache of the system catalog, in the Data Source Explorer right-click the subsystem and select Query Tuner > Refresh Catalog for Tuning.
Figure 50. The Open Summary Report option and a sample summary report
Figure 51. Refreshing the local cache of the system catalog
Capturing the environment of an SQL statement
When you are working with IBM Support to resolve a problem with tuning an SQL statement, or when you want to recreate the environment of an SQL statement on a different DB2 for z/OS subsystem, you can capture the statement's environment in a set of files. You can then upload the files to IBM Support or to the other subsystem.
Remember: This feature is available only when you are connected to a DB2 for z/OS subsystem. It is not available when you are connected to a DB2 for Linux, UNIX, and Windows database.
There are two areas in the workflow assistant where you can capture and send the environment of an SQL statement. The first area is in the upper-left corner of every page in the Capture section. In that location is the Capture Query Environment icon.
You can select a captured statement and click the icon to import the statement into the Query Environment window, You can also paste a statement into the window directly, or import a statement from a file.
Figure 52. The Capture Query Environment icon
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If a statement is particularly long and complex, including the creators and names of the tables that the statement references, which you can do in the Table information section, can aid IBM Support in understanding your problem better.
After specifying the SQL statement, click Next to specify options for the files that you will generate. If you plan to recreate the query environment on a DB2 for z/OS subsystem that is at a version different from the version of the currently connected subsystem, select the version of the target subsystem in the Convert for different version of DB2 for z/OS field.
If you are working with IBM Support and have a PMR number, type the number in the PMR or ETR Number field.
If you are recreating the query environment on another subsystem and are not working with IBM Support, you can just type zeros in the three entry fields for the PMR number.
Then, click the Generate Report button to create the files that can be used to recreate the query environment.
Figure 53. The Query Environment window
The files are listed in the Files to upload field. Ensure that the FTP settings are correct for the target location of the files. Then, click the Upload Files button.
Figure 54. The Generate Report button
Capturing the environment of an SQL statement 57
After you receive notification that the file transfer is complete, click Finish.
The second area in the workflow assistant where you can capture and send the environment of an SQL statement is in the Review section. After you run or attempt to run the Statistics advisor or to generate an access plan graph or reports, the Review section opens. On the left side of the workflow assistant is the Capture Query Environment option.
Figure 55. The Upload Files button
Clicking on the option opens the Collect data about the query environment page of the Review section. This page works almost identically to the Query Environment window. The first difference is that the SQL statement is not visible. The second difference is the layout. There are two subsections: Options and FTP Server Settings. In the first section, you can add information about tables referenced in the statement, set options for generating the files for recreating the environment, enter a PMR number, generate the report, and upload the files.
In the second section, you can specify the connection information for the target FTP server. This second section also lists the files that you generate.
Figure 56. The Capture Query Environment option in the Review section of the workflow assistant
Figure 57. The Options section in the Collect data about the query environment page of the Review section
Capturing the environment of an SQL statement 59
Figure 58. The FTP Server Settings section in the Collect data about the query environment page of the Review section
Additional resources Information center for IBM Data Studio
http://publib.boulder.ibm.com/infocenter/idmhelp/ds-v2r2/index.jsp
http://www.ibm.com/developerworks/forums/forum.jspa?forumID=1086
Optim™ Query Tuner for DB2 for Linux, UNIX, and Windows http://www-01.ibm.com/software/data/optim/query-tuner-luw/
Optim Query Tuner for DB2 for z/OS http://www-01.ibm.com/software/data/optim/query-tuner-z/
Optim Query Workload Tuner for DB2 for z/OS http://www-01.ibm.com/software/data/optim/query-workload- tuner-z/
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Configuring a DB2 for z/OS subsystem for query tuning
Setting global preferences
Tuning SQL statements
Additional resources

getting started with tuning sql statements in ibm data

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