Option | Description |
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Shared (per machine) (default) | Virtual users on each computer draw from a shared view of the datapool, with datapool rows apportioned to them collectively in sequential order, on a first-come-first-served basis. This option makes it likely that the virtual users or loop iterations will use data from different rows and that the server will see variable data. The exact row access order among all virtual users or iterations cannot be predicted, because this order depends on the test execution order and the duration of the test on each computer. |
Private | Each virtual user draws from a private view of the datapool, with datapool rows apportioned to each user in sequential order. This option ensures that each virtual user gets the same data from the datapool in the same order. However, because each user starts with the first row of the datapool and accesses the rows in order, different virtual users will use the same row. The next row of the datapool is used only if you add the test that is using the datapool to a schedule loop with more than one iteration. |
Segmented (per machine) | Virtual users on each computer draw from a segmented view of the datapool, with data apportioned to them collectively from their segment in sequential order, on a first-come-first-served basis. The segments are computed based on how a schedule apportions virtual users among computers. For example, if a schedule assigns 25% of users to group 1 and 75% to group 2, and assigns these groups to computer 1 and computer 2, the computer 1 view will consist of the first 25% of datapool rows and the computer 2 view will consist of the remaining 75% of rows. This option prevents virtual users from selecting duplicate values (for example, account IDs). If you disable wrapping, no row can be used more than once. |
By default, when a test reaches the end of a datapool or datapool segment, it reuses the data from the beginning. To force a test to stop at the end of a datapool or segment, clear the check box beside Wrap when the last row is reached. Forcing a stop might be useful if, for example, a datapool contains 15 records, you run a test with 20 virtual users, and you do not want the last five users to reuse information. Although the test is marked Fail because of the forced stop, the performance data in the test is still valid. However, if it does not matter to your application if data is reused, the default of wrapping is more convenient. With wrapping, you need not ensure that your datapool is large enough when you change the workload by adding more users or increasing the iteration count in a loop.
By default, one row is retrieved from the datapool for each execution of a test, and the data in the datapool row is available to the test only for the duration of the test. Select Fetch only once per user to specify that every access of the datapool from any test being run by a particular virtual user will always return the same row.
Datapool option | Iteration 1 | Iteration 2 |
---|---|---|
Sequential and Private | row 1 | row 2 |
Shared and Shuffled | row x | row y |
Fetch only once per user | row x | row x |