Choosing to Use Power Management

Powering off a desktop system may interfere with some operations that involve that machine. Take the following guidelines into account before deciding when to use system Power Management features on a desktop machine.

Electronic Mail Issues

Mail is not sent to any mail spool file on a machine while the machine is suspended. Typically, if mail cannot be delivered for more than three days, it is returned to the sender as undeliverable.

If you suspend your system for three days or longer, and your machine has a local mail spool, you may fail to receive items of mail that have been bounced back to the sender.

Mail Alias Issues

Mail aliases on a machine are not available to other users while that machine is suspended. If the machine is suspended long enough (typically three days), messages sent to an alias on that machine are bounced back to the sender.

Remote Login Issues

You cannot use rlogin(1) to connect to a machine while that machine is suspended. This command does not cause the machine to power on from a suspended state.

While your machine is suspended, you cannot access it by remote dial in.

Networked Software Issues

Suspend-Resume may have an impact on a networked application. A networked program may fail if it is not resilient when a peer system is suspended and does not respond to network traffic.

One example of this is when you run an Xhosted application from one system and display it on another system. If Power Management software suspends the latter system, the application software may fail.

Solstice AutoClient Issues

Do not use Suspend-Resume features on a machine that uses Solstice(TM) AutoClient(TM) software.

ATM Issues

Power Management software is not supported on SunATM(TM) devices. The ATM protocol is connection oriented, which means calls must be established between two endpoints (such as workstations) before data can be transferred. Each end of the call must maintain the connection actively, so neither end of an ATM connection can use Power Management software to suspend and then resume the connection later.

Cron Job Issues

Operations specified in a cron file do not run while a machine is suspended.

When the time arrives for a cron job to begin for a machine that is suspended, that job does not run at that time, nor is the job queued up to run later when that machine resumes.

Calendar Manager Issues

Calendar Manager does not display pop-up windows for scheduled events that occur while the desktop machine is suspended.

Thermal Stress Issues

The goal of Power Management is to conserve electricity. However, you should also take into account how an increase in power cycling will affect the overall reliability of the hardware.

Power Management software is active by default on sun4u systems (such as the Sun Ultra(TM) 1). Accordingly, the Power Management system for those machines is designed to evaluate each automatic power-cycle request that occurs due to the system being idle. If this evaluation determines that the thermal shock of power cycling on this occasion would contribute to decreasing hardware reliability, then this power-cycle request is deferred.

Despite this feature, you can still choose to turn off a sun4u system manually at any time. This checking feature is intended as a brake on the hardware being subjected to an excessive number of automatic power-cycle requests.