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This section includes the following topics:
- About the What-If tab
- How the What-If tab is structured
- How the What-If tab can help you identify performance enhancements
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The What-If tab lets you simulate the effect of creating, modifying, or dropping a B*Tree or bitmap index on the performance of all statements that Precise for Oracle has collected in the selected context, without physically making the change.
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See “About the Current tab” on page 51, “About the Activity tab” on page 61, and “About the SQL tab” on page 131.
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The What-If tab is slightly different in appearance from other tabs. It is divided into the following areas: Main area, Summary area, and Grid area.
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| Column | Description |
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 | Lets you launch to the SQL tab on the plan tab, if the statement was not evaluated, or the SQL tab on Compare tab, to compare the explain plan for this version of the statement with the original. See “About launching to SQL tab in context” on page 161. |
| Text | Portion of the SQL text. |
| In Oracle | Resource consumption of the impacted statement during the selected time frame. The format is: hh:mm:ss. Use this column to assess the heavy resource consuming statements that are either positively or negatively impacted. |
| Cost | Current estimated cost of the Oracle Optimizer, as taken from the latest explain plan. |
| Predicted Cost | Predicted cost of the Oracle Optimizer for the new plan. |
| Gain (%) | The amount in gain in percentage when performing the suggested index change. |
| Executions | Number of times the statement was executed during the selected time frame. |
| Statement | Name of the impacted statement. |
| Statement ID | The ID of the statement. |
| statement-username | The user name which executed the statement. |
| statement-explain-type | Display the explain type used for the recommendations. |
| Comment | Precise for Oracle may include its own comment on the simulated change, or why, for example, costs are not available. |
| Affected Transaction | The number of transactions for the specific statement that are affected by the index change. |
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You can identify a performance problem by doing one or more of the following:
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