VERITAS File System 3.5 (HP OnlineJFS/JFS 3.5) Administrator's Guide (August 2003)

Chapter 4
Application Interface
Freeze and Thaw
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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 29 and the vxtunefs (1M) manual page.