This topic discusses IOPs and IOAs that you must tag to perform specific functions for an i5/OS® logical partition if you partition your managed system using the HMC.
A tagged resource is an IOP or IOA that is selected because it controls a device that performs a specific function for a logical partition. The HMC and the i5/OS operating system use this tagging to locate and use the correct I/O device for each I/O function. For example, when you create an i5/OS partition profile, you must tag the I/O device that you want the i5/OS logical partition to use as its load source. The tag allows the HMC to locate the load source when you activate the logical partition using the partition profile.
You can tag either the IOP or the IOA that controls the I/O device that you want to use. Tagging the IOA allows you to specify the exact I/O device that you want to use. Tagging the IOP allows you to switch between devices on the IOP using control panel functions.
Some I/O device types are required to create an i5/OS logical partition, and other I/O device types are optional. For example, i5/OS always requires a load source from which you load the operating system. However, the alternate console device is used only if you use a twinaxial console as your primary console, so if you use another type of console as the primary console for i5/OS, you do not need to tag the alternate console device.
The following table lists and describes the device types that are tagged and indicates whether you are required to tag the device type to create an i5/OS partition profile on an HMC.
| Device | Description | Required to create i5/OS partition profile |
|---|---|---|
| Alternate restart device | Can be a tape drive or an optical device. The media in the alternate restart device is what the system uses to start from when you perform a D-mode initial program load (IPL). The alternate restart device loads the Licensed Internal Code contained on the removable media instead of the code on the load source disk unit. | Yes |
| Partition console | The first workstation that the system activates in the partition and the only device it activates on a manual IPL. The partition assumes that a console will always be available for use. | Yes (if you are using a console device other than the HMC) |
| Alternate console device | The twinaxial console device that the partition will look for if the primary console fails during a manual IPL. The alternate console device is used only when the primary console is twinaxial. | No |
| Operations Console direct connect device | An adapter used to support either a directly attached Operations Console or to support an asynchronous modem. This adapter does not apply to LAN-attached Operations Console. You can connect the Operations Console device to an external line so that your managed system can send information to your support provider if the managed system encounters problems. | No |
| Load source disk unit | Each i5/OS logical partition must have one disk unit designated as the load source. The system uses the load source to start the logical partition. The system always identifies this disk unit as unit number 1. | Yes |
If you use the Virtual Partition Manager to partition your managed system, you do not need to tag I/O devices for these I/O functions. The i5/OS logical partition automatically owns all physical I/O resources on the managed system, and the Virtual Partition Manager automatically tags the I/O device to use for each I/O function. The Virtual Partition Manager tags I/O devices for I/O functions based upon server model and location within the server. If you are partitioning a new server using the Virtual Partition Manager and have ordered the server with preloaded i5/OS, then you do not need to verify the placement of I/O devices within your new server. Otherwise, use the LPAR Validation Tool (LVT) to verify the placement of I/O devices within your server before using the Virtual Partition Manager to partition the server.