Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (F)
Guardian Procedure Calls Reference Manual—522629-013
5-125
FILE_OPEN_ Procedure
Disk File Considerations
•
Maximum number of concurrent nowait operations
The maximum number of concurrent nowait operations permitted for an open of a
disk file is 1. Attempting to open a disk file and specify a
nowait-depth value
greater than 1 causes FILE_OPEN_ to fail with an error 28.
•
Unstructured files
•
File pointers after an open
After a disk file is opened, the current-record and next-record pointers begin at
a relative byte address (RBA) of 0, and the first data transfer (unless
positioning is performed) is from that location. After a successful open, the
pointers are:
current-record pointer = 0D
next-record pointer = 0D
•
Sharing the same EOF pointer
If a given disk file is opened more than once by the same process, separate
current-record and next-record pointers are provided for each open, but all
opens share the same EOF pointer.
•
Structured files
•
Accessing structured files as unstructured files
The unstructured access option (
options.<0> = 1) permits a file to be
accessed as an unstructured file. Note that the block format used by Enscribe
must be maintained if the file is be accessed again in its structured form. (HP
reserves the right to change this block format at any time.) Refer to the
Enscribe Programmer’s Guide for information about Enscribe block formats.
For a file opened using the unstructured access option, a data transfer occurs
to the position in the file specified by an RBA (instead of to the position
indicated by a key address field or record number); the number of bytes
transferred is that specified in the file-system procedure call (instead of the
number of bytes indicated by the record format).
If a partitioned file, either structured or unstructured, is opened using the
unstructured access option, only the first partition is opened. The remaining
partitions must be opened individually with separate calls to FILE_OPEN_
(each call specifying unstructured access).
Accessing audited structured files as unstructured files is not allowed.