The ttymap command is run during system initialization to create the /var/adm/ttymap.data file. The /var/adm/ttymap.data file is used by the ttyname library function to search for terminal and terminal-related device files. The command populates /var/adm/ttymap.data with a list of device files indexed by device ID and filesystem ID, and with a time-stamped map of directories within /dev.
The ttyname(3C) library function attempts to find devices by lookup based on device number and filesystem ID. If a candidate with matching device and filesystem ID is found, ttyname checks its inode number. If no match is found, ttyname checks each directory in the map to see if it is newer than the time stamp in the /var/adm/ttymap.data file. If a newer directory is found, ttyname searches the directory for device files and recursively searches any newer subdirectories.
The /etc/ttysrch file can be used to specify directories that should be ignored, which decreases the size of the /var/adm/ttymap.data file, providing faster lookup, and to specify directories that contain clone devices, which allows ttyname to accept device files that do not match on inode number.