You can easily run multiple virtual machines concurrently. This may be useful if you are testing or trying to simulate many users accessing a shared resource or application. It is also useful when one VM is doing a long job, because you can work in another VM or in the host operating system while you wait for the job to complete.

You can start multiple VMs and guest operating systems in the following two basic ways:

• (Sequentially) You can start one VM using one configuration file, and at the end of that session, power off. (You have not pressed Exit, however, so the VMware application is still running.) Then you can point to a different configuration file, and power on to start a new session with a different VM or guest operating system.
• (Concurrently) You can start several VMs using different configuration files. For example, you might enter the vmware command three times specifying three different configuration files. You are running multiple VM instances concurrently and your screen display shows more than one VM window at any given time (unless you are using the VMs in full-screen mode).

When you are using multiple VMs concurrently keep the following guidelines in mind:

• Do not start multiple VMs using the same VM configuration file. If you need to run multiple VMs having the same definition, you should create copies of the desired configuration file, one for each VM that you want to run.
• Each VM should have its own unique hard drive. The only exceptions is if all shared drives are nonpersistent.
• CD-ROM and parallel devices are shareable. However, only one VM can have the device attached for access. The removable devices option (available through the main menu and the VMware Toolbox) allows you to attach and detach removable devices. You may need to first detach a device from one VM if you want a second VM to attach it.
• Floppy and serial devices are exclusive devices and cannot be shared by VMs.
• Only the first VM powered on can use the real-time clock RTC for high precision timing. If a subsequent VM requires the RTC, you should power off all VMs that were powered on before that VM, so that it gains access to the RTC.