What does 100% idle column mean in iostat –dx?

Question

linux

I'm trying to optimize my database on postgresql, I read that I should look at the idle column in iostat, I registered it on my server iostat –dx, but what does this command mean? And is it normal that my idle column is 99% full?

avg-cpu:  %user   %nice %system %iowait  %steal   %idle            
                             0.78    0.00    0.04    0.00    0.00   99.18  
Device             tps    kB_read/s

Answer 1

iostat, as surprising as its name may seem, shows statistics on I/O devices as well as CPUs.
The %idle you are interested in belongs to the avg-cpu section and as man iostat explains in plain text

%idle
Show the percentage of time that the CPU or CPUs were
idle and the system did not have an outstanding disk I/O
request.

This is the percentage of time that the CPU was idle.
That is, 99% idle - the system is actually not busy with anything.
Usually seen live in iostat -x 1