10-27-2009
HACMP terminology changed now and then. Some terms were used with older HACMP versions 3 and 4, some came into existence with the current HACMP Version 5 while others ceased to exist. The same is true with certain functions/possibilities. IBM Speak itself can be a bit challenging but when you mix up words from different times you end up in a mess.
An active-active cluster has (at least) two nodes and two Resource Groups RG. So there is one RG per node and only during takeover/failover two RG are on one node. This is a very good setup because during normal operation the RG (its application) has its dedicated CPU/RAM/IO. Furthermore not everybody can afford running (i.e. paying for) two servers but using only one. It does not at all mean that there is no takeover / failover possible.
A concurrent HACMP RG means Oracle RAC. I am not aware of another application that is able to run as a concurrent HACMP cluster. While there are two or more nodes active at a time this is not usually called an active-active configuration as no takeover is involved. In a concurrent cluster a node may die but the other(s) keep on working regardless.
Cascading / rotating is related to RG behaviour. If there is a fixed order of how the RG is taken over from node to node (usually in a Cluster with 3+ nodes that are different so that using certain nodes is perferable) this is a cascading behaviour. If the RG does not care on what node it is active, i.e. it can be active on any node a rotation of the RG might be OK.
Concurrent volume group are rarely used these days. Today you are likely to use Enhanced Concurrent Mode VG. And Oracle RAC can use an ECM VG in a Concurrent Cluster.
As you might have guessed by now already: some reading might be required. If you are an absolute beginner with HACMP you might start by reading the HACMP cookbook from December 2005 followed by the PowerHA cookbook (yes, the name changed with 5.5 ....) from September 09.
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LEARN ABOUT HPUX
cmhaltnode
cmhaltnode(1m) cmhaltnode(1m)
NAME
cmhaltnode - halt a node in a high availability cluster
SYNOPSIS
cmhaltnode [-f] [-v] [-t] [node_name...]
DESCRIPTION
cmhaltnode causes a node to halt its cluster daemon and remove itself from the existing cluster.
To halt cluster on the node, a user must either be superuser(UID=0), or have an access policy of FULL_ADMIN allowed in the cluster configu-
ration file. See access policy in cmquerycl.
When cmhaltnode is run on a node, the cluster daemon is halted and, optionally, all packages that were running on that node are moved to
other nodes if possible.
If node_name is not specified, the cluster daemon running on the local node will be halted and removed from the existing cluster.
If you issue this command while a cluster is still in the process of forming, the command will fail with the message "Unable to connect to
daemon." If this happens, wait for the cluster to form successfully, then issue the command again.
Options
cmhaltnode supports the following options:
-f Force the node to halt even if there are packages or group members running on it. The group members on the node will be
terminated. The halt scripts for all packages running on the node will be run; based on priority or dependency relation-
ships, this may affect packages on other nodes. In other words, packages on other nodes may either start or halt based on
this package halting. If the package configuration and current cluster membership permit, and if the package halt script
succeeds, the packages will be started on other nodes. Without this option, if packages are running on the given node,
the command will fail. If a package fails to halt, the node halt will also fail.
-v Verbose output will be displayed.
-t Test only. Provide an assessment of the package placement without affecting the current state of the nodes or packages.
This option validates the node's eligibility with respect to the package dependencies as well as the external dependencies
such as EMS resources, package subnets, and storage before predicting any package placement decisions. If there is a pack-
age in maintenance mode running on the nodes being halted, the package will always be halted and not failover to another
node; the report will not display an assessment for that package.
node_name...
The name of the node(s) to halt.
RETURN VALUE
cmhaltnode returns the following value:
0 Successful completion.
1 Command failed.
EXAMPLES
Halt the cluster daemon on two other nodes:
cmhaltnode node2 node3
AUTHOR
cmhaltnode was developed by HP.
SEE ALSO
cmquerycl(1m), cmhaltcl(1m), cmruncl(1m), cmrunnode(1m), cmviewcl(1m), cmeval(1m).
Requires Optional Serviceguard Software cmhaltnode(1m)