I use an AIX 4.3.3 and the /usr DataVolume is 87% occupied. Is this good ? What can i do to make some space ?
Also, how cand i defragment the hard drive ?

/usr should not change much so this should be nothing to worry about as long as you do not install any new software that uses /usr.

Checkout the defragfs command.

So can i uninstall some softwares to free up some space ? What software should i uninstall ?

Depends how much is left.
what is the output from
Look if there are some old kernels hanging around.

Do you need to free up some space in /usr?

/usr should not change on a normal stable system so unless you need to change something or install some new software, that needs to install into /usr, you have nothing to worry about.

On a stable system /usr at 90+ % would still be nothing to worry about.

Just checked my AIX workstation and /usr is at 96% and I have no worries about it, why would you?

On AIX you will typically find there is plenty of space left on the rootvg disks so if you do need to make a change, and need more space in /usr, then you can just increase the size as required from the currently unallocated disk space.

No, i don't need more space. I wast just worried . Thank you for your help.

Glad we could help.

/ (root), /var and /tmp are the ones you need to keep an eye on for AIX systems.

Typically /usr will stay the same unless you change (install) something.