Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (R)
Guardian Procedure Calls Reference Manual—522629-013
13-24
READLOCK[X] Procedures
pointer is set to the previous next-record pointer plus read-count. This process
repeats for each subsequent call to READLOCK[X].
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See “Considerations” for the READ procedure.
Considerations for READLOCKX Only
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The buffer and count transferred may be in the user stack or in an extended data
segment. The buffer and count transferred cannot be in the user code space.
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If the buffer or count transferred is in a selectable extended data segment, the
segment must be in use at the time of the call. Flat segments allocated by a
process are always accessible to the process.
•
The size of the transfer is subject to current restrictions for the type of file.
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If the file is opened for nowait I/O, and the buffer is in an extended data segment,
you cannot deallocate or reduce the size of the extended data segment before the
I/O completes with a call to AWAITIOX or is canceled by a call to CANCEL or
CANCELREQ.
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If the file is opened for nowait I/O, you must not modify the buffer before the I/O
completes with a call to AWAITIOX. This also applies to other processes that may
be sharing the segment. It is the application’s responsibility to ensure this.
•
If the file is opened for nowait I/O, and the I/O has been initiated with these
routines, the I/O must be completed with a call to AWAITIOX (not AWAITIO).
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If the file is opened for nowait I/O, a selectable extended data segment containing
the buffer need not be in use at the time of the call to AWAITIOX.
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Nowait I/O initiated with these routines may be canceled with a call to CANCEL or
CANCELREQ. The I/O is canceled if the file is closed before the I/O completes or
AWAITIOX 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 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.
Errors for READLOCKX Only
In addition to the errors currently returned from READLOCK, error 22 is returned from
READLOCKX when: