A temporary file system is an in-memory physical file system that supports in-storage mountable file systems. When a TFS is mounted on /tmp, it can be used as a high-speed file system for temporary files. This is useful for a large system with many shell users.
A TFS can range in size from 1MB to 1GB.
The drawback to making /tmp a TFS instead of an HFS is that if the system crashes, all temporary files -- including those created by the vi editor -- are lost. The vi editor writes temporary files to /tmp by default. To avoid this problem, in the /etc/rc file, set the TMP_VI shell environment variable to specify a different directory than /tmp.