Each test script data pool also contains a flag that indicates whether or not the test script must select a record when iterating through the records of the data pool.
Without the flag set, the data returned would be only the memory used within the running script, minus the memory-manager overhead.
如果不使用标记组，则返回的数据将只包括在运行脚本内使用的内存，减去内存管理器开销。
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If another transaction retrieves the data and sees that the flag is set by some other user, then it will, by convention, give a warning message to the user that the data is in use.