Run Time Mode
Index Advisor > Batch Run > Run Time Mode
The Batch Run is designed to give the most accurate result by providing options for obtaining the most accurate run time taking into account the effects of caching the data, indexes and the SQL statements. This section allows you to select one of the four options best suited to your SQL statement.
|Run to retrieve
Specify to retrieve the run time for processing All Records.
First n Records(s)
|Specify to retrieve the run time for processing n records where you specify the number of records retrieved.|
|Retrieve the run time by executing
Run SQL options
Select one of the following options:
- Run all SQL twice if original SQL runs faster than (seconds)—Combines the Original SQL twice and all others once and the All SQL twice options into one option and allows you to determine (by the number of seconds a SQL statement runs) which option to use. The original SQL statement always runs twice. The SQL alternatives run twice if the original SQL statement runs in less time than the value specified. Otherwise, the SQL alternatives all run once.
- First one twice using the second run time and others once—The first time you access data from table, the data is cached into memory. This process takes a few moments. The next time you access that data, it is already in memory so the following SQL statements run faster. So to have a comparable test, the first SQL statement is run twice and the time from the second run is compared to the time from the other statements.
- All once—For long running SQL statements, there is no need to run them twice since the effect from caching diminishes over time.
All twice—Running all SQL statements twice enables you to eliminate some factors that can affect the accuracy of the results. If some SQL statements have been recently executed, then the SQL information is likely to be resident in cache and it may execute faster because of that. Also, if the SQL statements use different indexes, some indexes may be resident in cache and the others are not.
Five methods of calculating the run time are available if you select this option: Excluding the first run time, Average, Sum, Maximum, and Minimum.
- Excluding the first run time—Specify to throw out the first run time and use the second one when all SQL statements should have the necessary items in cache. This minimizes the effect that caching of the SQL statement and the indexes may have on the accuracy of the run time results.
All multiple times—This option is suitable for SQL statements with very short run times. It executes the SQL statements the selected number of times. It calculates the run time based upon the selected calculation method. This option helps to negate the factor of other activity running on the CPU at the same time as the SQL is executed. Since the run time is calculated from the moment the SQL statement starts running to the time it finishes, if SQL statement shares the CPU with other activity, the run time includes this other activity. Four methods of calculating the run time are available if you select this option: Average, Sum, Maximum, and Minimum.
This option is only available for SELECT statements since the INSERT, UPDATE, and DELETE statements would need a rollback between each of the multiple executions.
Batch Run Schedule
Index Advisor > Batch Run > Batch Run Schedule
The Batch Run Schedule criteria enable you to schedule when to start and stop the Batch Run.
Specify to start the Batch Run immediately.
Date and Time
Specify to start the Batch Run at a specific date and time.
Specify to start the Batch Run after it has been running for a specified number of hours and minutes.
Specify to run the entire Batch Run until all SQL statements are executed.
Date and Time
Specify to terminate the Batch Run on the specified date and time.
Specify to terminate the Batch Run after it has executed a specified number of hours and minutes.
Terminate immediately (Date/Time and Duration only)
Specify to terminate the currently executing SQL statement and all remaining unexecuted SQL statements.
Terminate after currently executing SQL is finished (Date/Time and Duration only)
Specify to finish running the currently executing SQL statement and do not create the remaining indexes and benchmark the SQL statement against them.
View Batch Run Details
Index Advisor > Batch Run > View Batch Run Details
The Batch Run Details window displays a summary of the run time information of the SQL statements with the alternative indexes. The Batch Run Details window displays after the batch run process is completed unless the Show details on next batch run checkbox in the Batch Run Details window is unchecked.
You can review the Batch Run Details window after a Batch Run by selecting View | Show Batch Run Details when the Index Advisor window is active.
If a SQL statement has a database error during the Batch Run, an explanation of the error is included in the Batch Run details.