What is HMC?
HMC is a Linux based desktop PC workstation which is dedicated to a number of pSeries servers. It’s is used to manage LPARs. There can be several LPARs or a single full partition on physical pSeries server system. HMC provides GUI (Graphical User Interface) and CLI (Command Line Interface) to manage LPARs.

7040-681, 7040-671, 7039-651, 7038-6M2 etc. are some of the models of HMC.

Uses of HMC
HMC is used in a number of ways to manage LPARs. Few of its uses are listed below:

1. HMC is used to start, stop, reset and shutdown an LPAR.
2. pSeries servers systems can be booted started and stopped using HMC.
3. HMC can be used to open virtual console for every partition or pSeries server connected to the HMC. It looks like original console of the server.
4. HMC can be used to create partition profiles. Each profile contains information on processor, memory and I/O resources allocated to that particular partition. It also helps to switch between various profiles of LPAR. If you want to choose different profile for an LPAR, you need to reset the LPAR.
5. HMC can be used to carryout DLPAR operations between specific LPARs. This way memory, processor etc. resources can be allocated/de-allocated dynamically without the need to restart any LPAR.
6. Physical System resources and the status of system can be displayed by HMC.
7. HMC itself can be managed through its GUI and CLI tools.
8. HMC software level can be managed by HMC itself. That’s called microcode management.
9. Some problem determination and service support are also provided by HMC which include supports like call-home and error log notifications through phone line.

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Connection Interface For HMC
HMC connects to the server using serial interface and the protocol used is RS232. More serial ports to connect to multiple servers can be provided by Asynchronous Adapters

Credits

You may set your search path automatically each time you log in, by placing the appropriate “set path” command in your “.login” file.

(To learn more about the .login file, type “help dotlogin”.) Here is a sample of a command line that you might put in your .login file to set a non-standard search path:

set path = ( $path /usr/ucb /bin /usr/bin /usr/new .)

Of course, you can use vmstat with interval, but for those sysadmin folks who are use to using Top, its still more comfortable using (and seeing) the top output.

Topas is the equivalent of Top for AIX.. it’s better than Top as a matter of fact according to some AIX gurus (and Solaris)

If you persists in using top, You’ll have to build it yourself from the sources at http://www.unixtop.org/ plus probably this fix: 

        http://sourceforge.net/tracker/index.php?func=detail&aid=934590&group_id=72892&atid=536044

Good luck!