Choosing to Use Suspend-Resume

Powering off a desktop system may interfere with some operations that involve that machine. This section presents some guidelines to take into account before you 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 can not be delivered for more than three days, then the mail 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 might not receive messages that the mail application has sent 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 sent back to the sender.

Remote Login Issues

While your machine is suspended, you can not access the machine by remote dial-in. In other words, you can not use rlogin(1) to connect to a machine while that machine is suspended.

Networked Software Issues

The Suspend-Resume feature might have an impact on a networked application. A networked program might fail if the program 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 the application on a second system. If the Power Management software suspends the second system, the application software might fail.

Solstice AutoClient Issues

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

ATM Issues

The Power Management software is not supported on SunATM™ devices. The ATM protocol requires that 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 the Power Management software to suspend and, later, resume the connection.

Cron Job Issues

Operations specified in a cron file do not run during the time a machine is suspended.

When a system resumes, cron jobs scheduled to run during the time the system was suspended with the Power Management software are handled in the following way:

• The cron job scheduled to run earliest during the time the system was suspended is started as soon as the system resumes.

• Subsequent cron jobs that might have run during the time the system was suspended are not run at all.

Normally, the cron command identifies the next job to run and calculates the interval to wait to run that job. When a system resumes, the cron command calculates the interval until the first job has expired, then this already-queued cron job is run. The cron process then rechecks the queue of cron jobs. The cron process only considers jobs whose execution time has not yet passed, so any additional jobs whose run time fell during the time the system was suspended are not run.

Calendar Manager Issues

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

Thermal Stress Issues

The goal of the Power Management software is to conserve electricity. You should also take into account how an increase in power cycling affects the overall reliability of the hardware.

The Power Management software is active by default on sun4u systems, such as the Sun Ultra 1. Accordingly, the Power Management system for those machines evaluates each automatic power-cycle request that occurs due to the system being idle. If an evaluation determines that the thermal shock of power cycling on a particular occasion would decrease hardware reliability, then that power-cycle request is deferred.

Despite this feature, you can choose to turn off a sun4u system manually at any time. This checking feature prevents an excessive number of automatic power-cycle requests to the hardware.