Guardian Procedure Calls Reference Manual

◦ Nowait I/O initiated with this routine can be canceled with a call to CANCEL or
CANCELREQL. The I/O is canceled if the file is closed before the I/O finishes or
FILE_AWAITIO64_ is called with a positive time limit and specific file number, and the
request times out.
◦ A file opened by FILE_OPEN_ uses direct I/O transfers by default; you can use SETMODE
function 72 to force the system to use an intermediate buffer in the process file segment
(PFS) for I/O transfers. A file opened by OPEN uses a PFS buffer for I/O transfers, except
for large transfers to DP2 disks.
◦ If the extended address of the buffer is odd, bounds checking rounds the address to the
next lower word boundary and checks an extra byte as well. The odd address is used
for the transfer.
Disk File Considerations
• Large data transfers
Large data transfers (more than 4096 bytes), can be enabled by using SETMODE function
141. See Table 44 (page 1319).
• Record does not exist
If the position specified for the FILE_READUPDATE64_ operation does not exist, the call is
rejected with error 11. (The positioning is specified by the exact value of the current key and
current-key specifier.)
• Structured files
FILE_READUPDATE64_ without selecting a specific record
If the call to FILE_READUPDATE64_ immediately follows a call to FILE_SETKEY_ (or
KEYPOSITION[X]), the call to FILE_SETKEY_ (or KEYPOSITION[X]) must specify exact
◦
positioning mode in the positioning-mode parameter and the length of the entire key
in the length-word parameter.
If the call to FILE_READUPDATE64_ immediately follows a call to FILE_SETKEY_ (or
KEYPOSITION[X]) where a nonunique alternate key is specified, the FILE_READUPDATE64_
fails with an error 46 (invalid key). However, if an intermediate call to FILE_READ64_ or
FILE_READLOCK64_ is made, the call to FILE_READUPDATE64_ is permitted because a
unique record is identified.
◦ Indicators after FILE_READUPDATE64_
After a successful FILE_READUPDATE64_, the current-state indicators are unchanged
(current- and next-record pointers).
• Unstructured disk files
Unstructured files
For a FILE_READ64_ from an unstructured disk file, data transfer begins at the position
indicated by the current-record pointer. A call to FILE_READUPDATE64_ typically follows
◦
a call to FILE_SETPOSITION_ (or POSITION) that sets the current-record pointer to the
desired relative byte address.
◦ Pointer action for unstructured files is unaffected
◦ count-read for unstructured files
After a successful call to FILE_READUPDATE64_ to an unstructured file, the value returned
in count-read is determined by:
490 Guardian Procedure Calls (F)