HP-UX Reference (11i v1 00/12) - 5 Miscellaneous Topics, 7 Device (Special) Files, 9 General Information, Index (vol 9)

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STANDARD Printed by: Nora Chuang [nchuang] STANDARD
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v
vxfsio(7) vxfsio(7)
NAME
vxfsio - VxFS file system control functions
SYNOPSIS
#include <sys/types.h>
#include <sys/fs/vx_ioctl.h>
int ioctl(int fildes, int cmd, ... / arg /);
DESCRIPTION
The vxfs ioctl(2) enhancements provide for extended control over open files.
The argument fildes is an open file descriptor.
The data type and value of arg are specific to the type of command specified by cmd. Unless specified,
arg is treated as an int type. The symbolic names for commands and file status flags are defined by the
sys/fs/vx_ioctl.h header file.
The enhancements available are:
VX_SETCACHE
Set caching advisories. These advisories allow an application to indicate to the file system which
forms of caching are most advantageous.
NOTE: VX_SETCACHE is availablewith the HP OnLineJFS product only.
The values for arg are such that multiple advisories may be set by combining values with bitwise
OR operations. The possible values for arg are
VX_RANDOM
Indicates that the file is being accessed randomly. Read-ahead should not be performed.
VX_SEQ
Indicates that the file is being accessed sequentially. Maximum read-ahead should be per-
formed.
VX_DIRECT
Indicates that data associated with read and write operations is to be transferred directly to
or from the user supplied buffer, without being cached. When this option is enabled, all I/O
operations must begin on block boundaries and must be a multiple of the block size in
length. The buffer supplied with the I/O operations must be aligned to a word boundary.
If an I/O request fails to meet alignment criteria, the I/O request will be performed as a
data synchronous I/O operation.
VX_NOREUSE
Indicates that buffered data does not need to be retained in anticipation of further use by
the application.
VX_DSYNC
Indicates that data synchronous I/O mode is desired. In data synchronous I/O mode, a
write operation returns to the caller after the data has been transferred to external media,
but the inode is not updated synchronously if only the times in the inode need to be
updated.
VX_UNBUFFERED
Indicates that data associated with read and write operations is to be transferred directly to
or from the user supplied buffer, without being cached. The alignment constraints are
identical to those associated with the VX_DIRECT caching advisory.
If the file is extended or space is allocated to the file and the VX_UNBUFFERED advisory
is set, the inode is not written synchronously to disk before the write returns.
The
VX_RANDOM and VX_SEQ caching advisories are mutually exclusive. Similarly, only one of the
VX_DIRECT, VX_DSYNC,or VX_UNBUFFERED caching advisories may be set.
The VX_RANDOM, VX_SEQ, and VX_NOREUSE caching advisories are maintained on a per-file
basis. Changes made to these advisories by a process affect I/O operations by all processes currently
accessing the file.
HP-UX Release 11i: December 2000 1 Section 7189
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