From: WebSphere Development StudioILE COBOL Language Reference Version 5 SC09-2539-05
This READ can complete without returning any data in the following cases:
1. There are no invited devices and the timer function is not in effect. (This is the AT END condition.)
2. A controlled cancellation of the job occurs. This results in a file status value of 0A and a major-minor return code value of 0309.
3. The NO DATA phrase is omitted and the specified wait time expires. This results in a file status value of 00 and a major-minor return code value of 0310. The specified wait time is the value entered on the WAITRCD parameter for the file or the time interval specified on the timer function.
4. The NO DATA phrase is specified and there is no data immediately available when the READ is executed.