Page History
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You can view a statement that was saved in the PMDB. To open an existing statement1. On
- On the Precise bar, click Actions>Open.
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- In the Open Statement dialog box, choose the relevant properties for the statement you want to view from the Instance, Cabinet, Folder and Name drop-down lists, as follows:
- Instance Indicates the name of the instance that the statement belongs to.
- Cabinet Indicates the name of the cabinet that the statement is saved in (creates a cabinet if it does not already exist).
- Folder Indicates the name of the folder that the statement is saved in (creates a folder if it does not already exist).
- Name Indicates the name of the statement (generated randomly).
- Database Indicates the name of the database where the statement is running.
- User Indicates the statement's parsing user.
The statement's text is displayed in the text frame.
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- Click OK.
Editing an existing statement
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To edit an existing statement1. On
- On the Precise bar, click Actions>Edit.
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- In the Edit Statement dialog box, define the statement you want to edit by choosing a relevant property from the drop-down lists, as follows:
- Instance Indicates the name of the instance that the statement belongs to.
- Cabinet Indicates the name of the cabinet that the statement is saved in (creates a cabinet if it does not already exist).
- Folder Indicates the name of the folder that the statement is saved in (creates a folder if it does not already exist).
- Database Indicates the name of the database where the statement is running.
- User Indicates the statement's parsing user.
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- Enter a New Statement name in the Name field.
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- Edit the SQL text for the statement in the text frame.
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- Click OK.
The edited statement is saved in a logical cabinet and folder hierarchy.
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To re-explain an existing statement• Click , click the Re-Explain tab
Display the Sybase plan using Sybase SQL Advantage and Interactive SQL
You can display the Sybase plan using Sybase SQL Advantage and Interactive SQL. To display the Sybase plan using Sybase SQL Advantage and Interactive SQL• Click , click the Sybase Plan tab.
The Sybase SQL Advantage window is opened with the statement in context and commands to display its access path are executed.
How the SQL tab can help you identify performance problems
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You can identify a performance problem by doing one or more of the following:• See “Identifying
- Identifying problematic operators in the latest access
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- plan
- Locating referenced tables that pose potential
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- problems
- Examining
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- how access path changes affect statement
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- performance
- Locating
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- the most resource-consuming statements in a
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- batch
Identifying problematic operators in the latest access plan
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To identify problematic operators1. Launch
- Launch to the SQL tab with a statement in-context or open the statement you want to analyze in the SQL tab.
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- Open the Statistics tab in Plan view
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- Sort the grid by the Estimated Cost value (desc.)
NOTE The lower Estimated Cost the better.
Following are examples of how to improve problematic operators:• If
- If the operator is a Table Scan, try creating an index.
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- If the operator is of a Join type (such as Nested Loop or Merge), examine a different join method.
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- If the operator is a Sort operation, check if the sort is required by the application or can be removed. For example, remove distinct or change the union clause to union all.
See “About the Execution plan tree” on page 100.
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To locate reference tables that pose potential problems1. Launch
- Launch to the SQL tab with a statement in-context or open the statement you want to analyze in the SQL tab.
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- On the Plan tab, click Objects.
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- Click the Locator icon (to locate and highlight all the operators in the execution plan that access the specified table).
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- Examine the cost of these operators (to locate the problematic operators).
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- Identify the objects that are referenced by the problematic operators and try to tune those objects.
See “About viewing which objects are referenced by the execution plan” on page 103.
Examining how access path changes affect statement performance
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To examine how access path changes affect statement performance1. Launch
- Launch to the SQL tab with a statement in-context or open the statement you want to analyze in the SQL tab.
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- On the History tab, on the View controls, click History.
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- Analyze the statement's resource consumption over time vs. execution cost, access path changes, and number of executions over time. This can help you to observe whether the change in the statement performance occurred due to the change in the access path or not.
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- In the Changes History table, you can view additional details on the change made. You can select the launch icon for a particular access path and launch to the Plan tab in-context to continue your analysis of the change.
Locating the most resource-consuming statements in a batch
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To locate the most resource-consuming statements in a batch1. Launch
- Launch to the SQL tab with a statement in-context or open the statement you want to analyze in the SQL tab.
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- On the Statement tab, observe the access plan statements and their estimated cost.
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- Determine which of the statements has the highest estimated cost and focus your analysis on that statement.
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