TTY report

The two columns of TTY information (tin and tout) in the iostat output show the number of characters read and written by all TTY devices.

This includes both real and pseudo TTY devices. Real TTY devices are those connected to an asynchronous port. Some pseudo TTY devices are shells, telnet sessions, and aixterm windows.

Because the processing of input and output characters consumes CPU resources, look for a correlation between increased TTY activity and CPU utilization. If such a relationship exists, evaluate ways to improve the performance of the TTY subsystem. Steps that could be taken include changing the application program, modifying TTY port parameters during file transfer, or perhaps upgrading to a faster or more efficient asynchronous communications adapter.