Hmc Availability - IBM z13s Technical Manual

11.6.3 HMC availability

The HMC is attached to the same LAN as the server's and zBX Model 004 SEs. This LAN is
referred to as the
each CPC and with each zBX Model 004 SE.
If the z13s node is defined as a member of an ensemble, the primary HMC is the authoritative
controlling (stateful) component for the Unified Resource Manager configuration. It is also the
stateful component for policies that have a scope that spans all of the managed CPCs and
SEs in the ensemble. The managing HMC has an active role in ongoing system monitoring
and adjustment.
This configuration requires the HMC to be configured in a primary/alternate configuration. It
also cannot be disconnected from the managed ensemble members.
Failover: The primary HMC and its alternate must be connected to the same LAN
segment. This configuration allows the alternate HMC to take over the IP address of the
primary HMC during failover processing.
11.6.4 Considerations for multiple HMCs
Customers often deploy multiple HMC instances to manage an overlapping collection of
systems. Until the emergence of ensembles, all of the HMCs were peer consoles to the
managed systems. Using this configuration, all management actions are possible to any of
the reachable systems while logged in to a session on any of the HMCs (subject to access
control). With the Unified Resource Manager, this paradigm has changed. One ensemble is
managed by one primary and alternate HMC pair. Multiple ensembles require an equal
number of primary and alternate HMC pairs to manage them. If a z13s server, a zEnterprise
System, or a zBX Model 004 is added to an ensemble, management actions that target that
object can be done only from the managing (primary) HMC for that ensemble.
11.6.5 HMC browser session to a primary HMC
A remote HMC browser session to the primary HMC that manages an ensemble allows an
user who is logged on to another HMC or a workstation to perform ensemble-related actions.
11.6.6 HMC ensemble topology
The system management functions that pertain to an ensemble use the HMC and the z13s,
zEnterprise System, or zBX Model 004 SEs through the internode management network
(INMN) to provide the required connectivity.
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Customer Managed Management Network
. The HMC communicates with