Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (F)
Guardian Procedure Calls Reference Manual—522629-013
5-38
FILE_CREATE_ Procedure
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Odd unstructured files
An odd unstructured file permits reading and writing of odd byte counts and
positioning to odd byte addresses.
If
options.<15> is 1 and file-type is 0, an odd unstructured file is created. In
that case, the values of
record-specifier, read-count, and write-count
are all interpreted exactly; for example, a
write-count or read-count of 7
transfers exactly 7 bytes.
•
Even unstructured files
If
file-type is 0 and options.<15> is 0, an even unstructured file is created. In
that case, the values of
read-count and write-count are each rounded up to
an even number; for example, a
write-count or read-count of 7 is rounded up
to 8, and 8 bytes are transferred.
An even unstructured file must be positioned to an even byte address; otherwise,
the FILE_GETINFO_ procedure returns error 23 (bad address).
If you use the File Utility Program (FUP) CREATE or HP Tandem Advanced
Command Language (TACL) CREATE command to create a file, it creates an even
unstructured file by default.
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Upper limit for maximum-extents
There is no guarantee that a file will be created successfully if you specify a value
greater than 500 for
maximum-extents. In addition, FILE_CREATE_ returns
error 21 if the values for
primary-extent-size, secondary-extent-size,
and
maximum-extents yield a file size greater than (2**32) - 4096 bytes
(approximately four gigabytes) or a partition size greater than 2**31 bytes (two
gigabytes).
In addition, it is not always possible to allocate all of the extents specified by
maximum-extents. The actual number of extents that can be allocated depends
on the amount of space in the file label. If there are alternate keys or partitions, the
maximum number of extents allowed is less than 978. If you specify
MAXEXTENTS, you must also consider the primary and secondary extent sizes to
avoid exceeding the maximum file size.
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Disk accesses and the refresh EOF option
If a disk file has the refresh EOF option set (
options.<10> = 1), the file label is
immediately written to disk each time the end-of-file (EOF) pointer is changed.
(For a description of the refresh EOF option, see the information on unstructured
disk files in the
Enscribe Programmer’s Guide.) Depending on the particular
application, there can be a significant decrease in processing throughput due to
the increased number of disk writes when the refresh EOF option is set.
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Creating a HP NonStop™ Storage Management Foundation (SMF) file