Introduction to the HMC

This section briefly describes some of the concepts and functions of the Hardware Management Console (HMC) and introduces the user interface that is used for accessing those functions.

The HMC allows you to configure and manage servers. One HMC can manage multiple servers, and dual HMCs can provide redundant support by managing the same system. To ensure consistent function, each HMC is shipped preinstalled with the HMC Licensed Machine Code Version 8, Release 1.

To provide flexibility and availability, you can implement HMCs in several configurations.

HMC as the DHCP server

An HMC that is connected by either a private network to the systems it manages might be a DHCP server for the service processors of the systems. An HMC might also manage a system over an open network, where the managed system's service processor IP address has been assigned by a customer-supplied DHCP server or manually assigned using the Advanced System Management Interface (ASMI).

Physical proximity

Prior to HMC version 7, at least one local HMC was required to be physically located near the managed systems. This is not a requirement with the Version 7 and the HMC's web browser interface. The local device must be in the same room and within 8 m (26 ft.) of your server. The local device must have the functional capability that is equivalent to the HMC that it replaces and that is needed by the service representative to service the system. For a virtual HMC, the functional capabilities also include the means of transferring service data, such as firmware updates or diagnostic data, and logs to and from the HMC.

Redundant or Dual HMCs

A server might be managed by either one or two HMCs. When two HMCs manage one system, they are peers, and each HMC can be used to control the managed system. The best practice is to attach one HMC to the service networks or HMC ports of the managed systems. The networks are intended to be independent. Each HMC might be the DCHP server for a service network. Because the networks are independent, the DHCP servers must be set up to provide IP addresses on two unique and nonroutable IP ranges.

Redundant or Dual HMCs that manage the same server must not be at different version and release levels. For example, an HMC at Version 7 Release 7.1.0 and an HMC at Version 7 Release 3.5.0 cannot manage the same server. The HMCs must be at the same version and release level.

When the server is connected to the higher version of the management console, the partition configuration is upgraded to the latest version. After the partition configuration upgrade, lower levels of the management consoles will not be able to interpret the data correctly. After the server is managed by the higher version of the management console, you must first initialize the server before you can go back to the lower version of the management console. You can restore a backup that is taken at the older level or re-create the partitions. If the server is not initialized, one of the following outcomes can occur depending on the version of the lower-level HMC:

• HMC Version 7 Release 7.8.0 and later reports a connection error of Version mismatch with reference code Save Area Version Mismatch.
• HMC Version 7 Release 7.7.0 and earlier might report a server state of Incomplete or Recovery. In addition, partition configuration corruption can also occur.