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Volume label fields<br />
Table 22. Volume Label Fields<br />
Offset Data Type Length Contents <strong>File</strong> Type<br />
0 Character 128 Volume label of current volume. Diskette, tape<br />
128 Character 128 Header label 1 of the opened file. Diskette, tape<br />
256 Character 128 Header label 2 of the opened file. Tape<br />
I/O feedback area<br />
AS/400 uses OS/400 messages and I/O feedback information to communicate the<br />
results of I/O operations to the program. The system updates the I/O feedback<br />
area for every successful I/O operation unless your program uses blocked record<br />
I/O. In that case, the system updates the feedback area only when it reads or<br />
writes a block of records. Some of the information reflects the last record in the<br />
block. Other information, such as the count of I/O operations, reflects the number<br />
of operations on blocks of records and not the number of records. See your<br />
high-level language information to determine if your program uses blocked record<br />
I/O.<br />
The I/O feedback area consists of two parts: a common area and a file-dependent<br />
area. The file-dependent area varies by the file type.<br />
Common I/O feedback area<br />
Table 23. Common I/O Feedback Area<br />
Offset Data Type Length Contents<br />
0 Binary 2 Offset to file-dependent feedback area.<br />
2 Binary 4 Write operation count. Updated only when a write<br />
operation completes successfully. For blocked record I/O<br />
operations, this count is the number of blocks, not the<br />
number of records.<br />
6 Binary 4 Read operation count. Updated only when a read<br />
operation completes successfully. For blocked record I/O<br />
operations, this count is the number of blocks, not the<br />
number of records.<br />
10 Binary 4 Write-read operation count. Updated only when a<br />
write-read operation completes successfully.<br />
14 Binary 4 Other operation count. Number of successful operations<br />
other than write, read, or write-read. Updated only when<br />
the operation completes successfully. This count includes<br />
update, delete, force-end-of-data, force-end-of-volume,<br />
change-end-of-data, release record lock, and<br />
acquire/release device operations.<br />
18 Character 1 Reserved.<br />
Appendix A. Feedback area layouts 179
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