VERITAS File System 4.1 Administrator's Guide

Application Interface
Freeze and Thaw
Chapter 484
Freeze and Thaw
The VX_FREEZE ioctl command is used to freeze a file system. Freezing a file system
temporarily blocks all I/O operations to a file system and then performs a sync on the file
system. When the VX_FREEZE ioctl is issued, all access to the file system is blocked at the
system call level. Current operations are completed and the file system is synchronized to
disk. Freezing provides a stable, consistent file system.
When the file system is frozen, any attempt to use the frozen file system, except for a VX_THAW
ioctl command, is blocked until a process executes the VX_THAW ioctl command or the
time-out on the freeze expires.
Get I/O Parameters ioctl
VxFS provides the VX_GET_IOPARAMETERS ioctl to get the recommended I/O sizes to use on
a file system. This ioctl can be used by the application to make decisions about the I/O sizes
issued to VxFS for a file or file device. For more details on this ioctl, refer to the vxfsio (7)
manual page. For a discussion on various I/O parfCameters, refer to Chapter 2, “VxFS
Performance: Creating, Mounting, and Tuning File Systems,” on page 37 and the vxtunefs
(1M) manual page.