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The open feedback area also contains information about each device or<br />
communications session that is defined for the file.<br />
v Input/output feedback area<br />
There are two sections of the I/O feedback area that are updated on the<br />
successful completion of input and output operations:<br />
– Common area<br />
This area contains information about I/O operations that were performed on<br />
the file. This includes the number of operations and the last operation<br />
performed. See “I/O feedback area” on page 179 for a complete list of the<br />
information that you can retrieve from the common I/O feedback area.<br />
– <strong>File</strong>-dependent feedback area<br />
This area contains file-specific information for display, database, printer, and<br />
ICF files; for example, the major and minor return code and amount of data<br />
received from the device. See “I/O feedback area for ICF and display files” on<br />
page 185, “I/O feedback area for printer files” on page 188, and “I/O<br />
feedback area for database files” on page 189 for a complete list of the<br />
information that you can retrieve from the file-dependent I/O feedback area.<br />
The above information areas can be useful to you. For example, when an error<br />
occurs with a device file, the program could determine predefined error handling<br />
operations based on the major/minor return code in the file-dependent feedback<br />
area. If data is being received from a communications device and the application<br />
on the other end sends an error, the program could determine that the next<br />
operation should be to wait until the next block of data is sent indicating the error.<br />
Possibly, the next operation may be to close the file and end the conversation with<br />
the application on the other side or wait for the next request from the application.<br />
Another way might include detecting the type of file that actually opened to<br />
determine the type of operations that are allowed. If the file type is printer, only<br />
output operations are allowed.<br />
<strong>File</strong> error detection and handling by the system<br />
24 <strong>File</strong> <strong>Management</strong> V4R5<br />
The system can detect errors when a file is opened, when a program device is<br />
acquired or released, during I/O operations to a file, and when the file is closed.<br />
When appropriate, the system will automatically try to run a failing operation<br />
again, up to a retry limit. When a retry is successful, neither operator nor program<br />
action is required.<br />
How the system reports errors:<br />
The system reports errors that can affect the processing of the program in any or<br />
all of the following ways:<br />
v A notify, status, diagnostic, or escape message may be sent to the program<br />
message queue of the program using the file. These messages may also appear<br />
in the job log, depending on the message logging level that is set for the job. See<br />
“Messages and message monitors in files by the system” on page 25 for more<br />
information.<br />
v The high-level language may return a file status code.<br />
v A major and minor return code is returned in the I/O feedback area for<br />
intersystem communications function (ICF), display, and printer files. See “Major<br />
and minor return codes in files by the system” on page 26 for more information.
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