Purpose
Changes a previously-defined communication
group for a peer domain.
Syntax
To change an attribute of a communication
group:
chcomg [ -s sensitivity ] [ -p period ] [ -g grace ] [ -t priority ] [-b] [-r]
[ -x b | r | br ] [ -e NIM_path ] [ -m NIM_parameters ]
[ -N UseForNodeMembership ] [-h] [-TV] communication_group
To change a reference in a heartbeat interface resource
to a different communication group:
chcomg [ -i h:heartbeat_interface1[:node1 ] [ ,heartbeat_interface2[:node2]...] | -S h:"heartbeat_interface_selection_string" ] [ -h ] [ -TV ] communication_group
To change a reference in a network interface resource to
a different communication group:
chcomg [-i n:network_interface1[:node1][,network_interface2[:node2]...] │ -S n:"network_interface_selection_string"] [ -6 ] [-h] [-TV] communication_group
Description
The chcomg command changes an existing communication group definition
with the name specified by the communication_group parameter for the online peer domain. The communication
group is used to define heartbeat rings for use by topology services
and to define the tunables for each heartbeat ring. The communication
group determines which devices are used for heartbeating in the peer
domain.
The chcomg command must
be run on a node that is currently online in the peer domain where
the communication group is defined. One or more attributes can be
changed with one chcomg command, but at
least one change is required.
The -e and -m flags are used to set the network
interface module (NIM) path and parameters. The NIM path is the path
to the NIM that supports the adapter types used in the communication
group. The NIM parameters are passed to NIM when it is started.
The chcomg command can also be used
to assign a communication group to an interface resource. Use the -i flag to assign the communication group to
a specific interface resource name. The interface resource can be
limited to one on a particular node. An interface resource can also
be specified using the -S flag and a selection
string. This is used when specifying the interface resource name
is not sufficient. Before a communication group can be removed, any
interface resources that refer to it must be reassigned.
More
than half of the nodes must be online to change a communication group
in the domain.
Flags
- -s sensitivity
- Specifies the heartbeat sensitivity. This is the number of missed
heartbeats that constitute a failure. The sensitivity is an integer
greater than or equal to 4.
- -p period
- Specifies the period, which is the number of seconds between heartbeats.
The value of period can be an integer or
a floating-point number that is greater than or equal to 1.
- -g grace
- Specifies the grace period that is used when heartbeats are no
longer received. When a heartbeat is missed, an Internet Control Message
Protocol (ICMP) echo packet is sent to the failed node. If the echo
is returned, the grace period is initiated.
The grace period is
specified in seconds and is significant to milliseconds. It can be
specified as an integer, a floating-point number, or one of these
values:
- 0
- Specifies that the grace period is disabled.
- -1 | d
- Specifies that the topology services subsystem controls the grace
period. This is the default value.
- -t priority
- Specifies the priority. The priority indicates the importance
of this communication group with respect to others. It is used to
order the heartbeat rings. The lower the number, the higher the priority.
The highest priority is 1.
- -b
- Specifies that broadcast will be used if the underlying media
support it. The -b flag cannot be used
when specifying -x b.
- -r
- Specifies that source routing will be used if the underlying media
support it. The -r flag cannot be used
when specifying -x r.
- -x b | r | br
- Excludes control for the heartbeat mechanism. This indicates that
one or more controls for heartbeat mechanisms should not be used even
if the underlying media support it. The following can be excluded:
- b
- Specifies that broadcast should not be used even if the underlying
media support it.
- r
- Specifies that source routing should not be used even if the underlying
media support it.
Excluding more than one control is specified by listing
the feature option letters consecutively (-x br).
- -i h | n:network_interface1[:node1] [,network_interface2[:node2]...
- Assigns this communication group to the network interface resource
defined by the network interface resource name and optionally the
node name where it can be found. Specify -i h for heartbeat
interface resources or -i n for network interface resources.
By default, the -i n flag adds network interface resources
that have IPv4 addresses to communication_group. If the -6 flag is specified, the -i n flag adds network interface
resources that have IPv6 addresses to communication_group.
If -i is specified, -S cannot be specified.
- -S h | n: "network_interface_selection_string"
- Assigns this communication group to the interface specified by
the network interface selection string. Specify -S h for heartbeat
interfaces or -S n for network interfaces. By default, the -S n flag adds network interface resources that have IPv4 addresses
to communication_group. If the -6 flag is specified,
the -S n flag adds network interface resources that have IPv6
addresses to communication_group.
If -S is specified, -i cannot be specified.
- -e NIM_path
- Specifies the network interface module (NIM) path name. This character
string specifies the path name to the NIM that supports the adapter
types in the communication group.
- -m NIM_parameters
- Specifies the NIM start parameters. This is a character string
that is passed to the NIM when starting it.
- -N UseForNodeMembership
- Specifies whether group services use the communication group in
calculating node membership. Sets the UseForNodeMembership persistent
resource attribute for the communication group resource. Valid values
are:
- 0
- Indicates that, regardless of the results of liveness checks run
on NetworkInterface resources that are members of this communication
group, group services do not use those results in calculating whether
the node owning the interfaces is online.
- 1
- Indicates that group services use the results of liveness checks
run on the NetworkInterface resources in calculating the online
state of their owning nodes.
- -6
- Specifies that IPv6 addresses represented as resources on each
interface have their communication group changed to the one specified.
IPv4 addresses represented as resources on the interfaces are unaffected.
By default (without the -6 flag specified), the inverse is
true. Only IPv4 addresses represented as resources on the interface
have their communication group changed.
- -h
- Writes the command's usage statement to standard output.
- -T
- Writes the command's trace messages to standard error. For your
software service organization's use only.
- -V
- Writes the command's verbose messages to standard output.
Parameters
- communication_group
- Specifies the name of an existing communication group to be changed
in the peer domain.
Security
The user of the chcomg command needs write permission for the IBM.CommunicationGroup resource class. Write permission for the IBM.NetworkInterface resource class is required to set the communication group
for a network interface resource. By default, root on any node in the peer domain has read and write access
to these resource classes through the configuration resource manager.
Exit Status
- 0
- The command ran successfully.
- 1
- An error occurred with RMC.
- 2
- An error occurred with a command-line interface script.
- 3
- An incorrect flag was entered on the command line.
- 4
- An incorrect parameter was entered on the command line.
- 5
- An error occurred that was based on incorrect command-line input.
Environment Variables
- CT_CONTACT
- Determines the system where the session with the resource monitoring
and control (RMC) daemon occurs. When CT_CONTACT is set to a host
name or IP address, the command contacts the RMC daemon on the specified
host. If CT_CONTACT is not set, the command contacts the RMC daemon
on the local system where the command is being run. The target of
the RMC daemon session and the management scope determine the resource
classes or resources that are processed.
- CT_IP_AUTHENT
- When the CT_IP_AUTHENT environment variable exists, the RMC daemon
uses IP-based network authentication to contact the RMC daemon on
the system that is specified by the IP address to which the CT_CONTACT
environment variable is set. CT_IP_AUTHENT only has meaning if CT_CONTACT
is set to an IP address; it does not rely on the domain name system
(DNS) service.
Restrictions
This command must be run on
a node that is defined and online to the peer domain where the communication
group is to be changed.
Implementation Specifics
This command is
part of the Reliable Scalable Cluster Technology (RSCT) fileset for AIX®.
Standard Input
When the -f
"-" or -F "-" flag
is specified, this command reads one or more node names from standard
input.
Standard Output
When the -h flag is specified, this command's usage statement is written
to standard output. All verbose messages are written to standard
output.
Standard Error
All trace messages are written
to standard error.
Examples
In these examples, node
nodeA is defined and online to peer domain
ApplDomain.
- To change the communication group ComGrp1 for ApplDomain to a sensitivity of 4 and period of 3, run this command on nodeA:
chcomg -s 4 -p 3 ComGrp1
- To change the communication group ComGrp1 for ApplDomain to use broadcast, run
this command on nodeA:
chcomg -b ComGrp1
- To change the communication group ComGrp1 for ApplDomain to no longer use source
routing, run this command on nodeA:
chcomg -x r ComGrp1
- To change the communication group ComGrp1 for ApplDomain, to use a NIM path of /usr/sbin/rsct/bin/hats_nim, and to use NIM parameters
-l 5 to set the logging level, run this
command on nodeA:
chcomg -e /usr/sbin/rsct/bin/hats_nim -m "-l 5" ComGrp1
- To assign the communication group ComGrp1 for ApplDomain to the heartbeat interface
resource named hbi0 on nodeC, run this command on nodeA:
chcomg -i h:hbi0:nodeC ComGrp1
- To assign the communication group ComGrp1 for ApplDomain to the heartbeat interface
resource named eth0 on nodeB, run this command on nodeA:
chcomg -i n:eth0:nodeC ComGrp1
- To assign the communication group ComGrp1 for ApplDomain to the heartbeat interface
resource that uses the subnet 9.345.67.812, run this command on nodeA:
chcomg -S h:"Subnet == '9.345.67.812'" ComGrp1
- To assign the communication group ComGrp1 for ApplDomain to the network interface
resource that uses the subnet 9.123.45.678, run this command on nodeA:
chcomg -S n:"Subnet == '9.123.45.678'" ComGrp1
- To change the communication group ComGrp1 for ApplDomain to a period of 500 milliseconds, run this command on nodeA:
chcomg -p 0.5 ComGrp1
Location
- /usr/sbin/rsct/bin/chcomg