Veritas™ File System Programmer's Reference Guide - Solaris

Other advisories

The VX_SEQ advisory is a per-file advisory that indicates that the file is accessed sequentially. A process setting this advisory on a file through its file descriptor impacts the access pattern of other processes currently accessing the same file. When a file with the VX_SEQ advisory is read, the maximum read-ahead is performed. When a file with VX_SEQ advisory is written, sequential write access is assumed and the modified pages with write operations are not immediately flushed. Instead, modified pages remain in the system page cache and those pages are flushed at some distance point behind the current write point (flush behind).

The VX_RANDOM advisory is a per-file advisory that indicates that the file is accessed randomly. A process setting this advisory on a file through its file descriptor impacts the access pattern of other processes currently accessing the same file. This advisory disables read-ahead with read operations on the file, and disables flush-behind on the file. The result of disabling flush behind is that the modified pages in the system page cache from the recent write operations are not flushed to the disk until the system pager is scheduled and run to flush dirty pages. The rate at which the system pager is scheduled is based on availability of free memory and contention.