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Cluster Management and Administration 165
Lazy Update has some limitations, which you need to consider when you rely
on Lazy Update in general:
• If the first disk in a sharedvg has been replaced, the
importvg command
will fail as Lazy Update expects to be able to match the hdisk number for
the first disk to a valid PVID in the ODM.
• Multi-LUN support on the SCSI RAID cabinets can be very confusing to
Lazy Update as each LUN appears as a new hdisk known to only one
node in the cluster (remember that Lazy Update works on LVM
constructs).
8.4.3 C-SPOC
The Cluster Single Point of Control (C-SPOC) utility lets system
administrators perform administrative tasks on all cluster nodes from any
node in the cluster. These tasks are based on commonly performed AIX
system administration commands that let you:
• Maintain user and group accounts (see 8.8, “User Management” on page
178).
• Maintain shared Logical Volume Manager (LVM) components.
• Control HACMP services on a cluster-wide basis (see Chapter 8.2,
“Starting and Stopping HACMP on a Node or a Client” on page 154).
Without C-SPOC functionality, the system administrator must spend time
executing administrative tasks individually on each cluster node. Using the
C-SPOC utility, a command executed on one node is also executed on other
cluster nodes. Thus C-SPOC minimizes administrative overhead and reduces
the possibility of inconsistent node states. For example, to add a user, you
usually must perform this task on each cluster node. Using C-SPOC,
however, you issue a C-SPOC command once on a single node, and the user
is added to all specified cluster nodes.
C-SPOC also makes managing logical volume components and controlling
cluster services more efficient. You can use the C-SPOC utility to start or stop
cluster services on nodes from a single node.
C-SPOC provides this functionality through its own set of cluster
administration commands, accessible through SMIT menus and screens. To
use C-SPOC, select the Cluster System Management option from the
HACMP for AIX menu. See the
HACMP for AIX, Version 4.3: Administration
Guide, SC23-4279
for detailed information on using C-SPOC SMIT options.
With C-SPOC, you can perform the following tasks: