Use this task to configure communication between core groups
that are in the same cell.
About this task
A cell, by default, contains a single core group, called
DefaultCoreGroup. All processes in the cell are initially members
of this core group. A single core group is usually sufficient. However,
some topologies or special circumstances require multiple core groups.
For example, the optimal number of servers in a core group is typically
around 50. If the number of members in a core group exceeds this optimal
number, you might need to create one or more additional core groups.
If
you need to define multiple core groups within a cell, you should
configure core group bridges between those core groups. If you do
not configure these core group bridges, each core group is isolated
from the other core groups in the cell.
After you configure
the core group bridges between the core groups in a cell, each core
group member can use the bridges to share its availability status
with all of the other members of the configured core groups in that
cell.
Avoid trouble: When
configuring core group bridges, remember the following requirements:
- Whenever a change is made in core group bridge configuration,
including the addition of a new bridge, or the removal of an existing
bridge, you must fully shutdown, and then restart all core group bridges
in the affected access point groups.
- There must be at least one running core group bridge in each core
group. If you configure two bridges in each core group, a single server
failure does not disrupt the bridge functionality. Also, configuring
two bridges enables you to periodically cycle out one of the bridges.
If all the core group bridges in a core group are shutdown, the core
group state from all foreign core groups is lost.
gotcha
Best practice: It
is also recommended that:
- Core group bridges be configured in their own dedicated server
process, and that these processes have their monitoring policy set
for automatic restart.
- For each of your core groups, you set the IBM_CS_WIRE_FORMAT_VERSION
core group custom property to the highest value that is supported
on your environment.
- To conserve resources, do not create more than
two core group bridge interfaces when you define a core group access
point. You can use one interface for workload purposes and another
interface for high availability. Ensure that these interfaces are
on different nodes for high availability purposes. For more information,
see the frequently asked question information on core group bridges.
bprac
Complete the following actions to configure communication
between core groups that are in the same cell.
- Configure an access point group to define the core groups
that need to communicate.
An access point group contains
the core group access points for the core groups that need to communicate.
Core group access points define the set of servers that provide access
to the core group. To configure communication between core groups
that are in the same cell, you can choose an existing access point
group, such as the DefaultAccessPointGroup, which is created by default,
or you can create a new access point group. To create a new access
point group, complete the following steps:
- In the administrative console, click .
- Enter a name for the access point group that is unique
within the cell.
- Add core group access points to your access point group.
Choose any available core group access points for the core
groups that need to communicate in the cell. A default core group
access point is automatically created whenever a core group is created.
Therefore, you should never have to create core group access points.
The access point group that you create must have a core group access
point for each core group in the cell that needs to communicate.
Best practice: When you configure communication
between core groups in a single cell, you do not have to add any peer
access points to an access point group Refer to the topic
Configuring
the core group bridge between core groups that are in different cells for
more information about configuring communication between cells.
bprac
If
you use an existing access point group, choose an access point group
that does not have peer access points. To configure an existing access
point group, complete the following steps:
- In the administrative console, click . Your current configuration with any existing
access point groups is displayed.
- Click access_point_group_name.
- Add core group access points to your access point group.
Choose any available core group access points for the core groups
that need to communicate.
- Create bridge interfaces for each core group access point.
The bridge interfaces that you add provide access to the
designated core group. Create at least one bridge interface for each
core group access point. To ensure the availability of a core group
access point, it is recommended that you configure two bridge interfaces
for each access point.
Avoid trouble: Even though
it is possible to define multiple access points for a core group,
you should only define a single access point to represent each core
group
gotcha
- In the administrative console, click access_point_group_name.
- Click the name of a core group access point in the access
point group, and then click Show Detail.
- To create a new bridge interface, click .
- Select a server to be the bridge interface.
Best practice: A server that you
select as a core group bridge interface should not be a server that handles
production responsibilities, such as filtering requests to cluster members,
or WebSphere proxy servers. Any server that is a core group bridge interface
experiences extensive memory and CPU usage during core group bridge startup,
and failover processing, which occurs when one of the bridges in a core group
stops. If you cannot dedicate a server as a core group bridge interface, you
should select a node agent as your core group bridge interface.
bprac
- Repeat these steps to create bridge interfaces for each
core group access point in your access point group.
- Optional: Configure the high
availability manager protocol to establish transparent bridge failover
support.
When a core group bridge server restarts, state
information, such as WLM data, and ODR or WebSphere Application Server
proxy server routing data, is lost until the state information is
recovered by a bridge in the same core group. The length of time the
data is lost varies depending on the number of core groups and the
amount of state data, but the length of time can be a minute or longer.
During this time, ODRs and WebSphere Application Server proxy servers
might report 503 errors, and JNDI look-ups for objects in remote core
groups might fail.
If you are running on Version 7.0.0.1 or
later, you can avoid such outages, if you enable the transparent bridge
failover protocol by setting the IBM_CS_HAM_PROTOCOL_VERSION custom
property to 6.0.2.31 in each core group. When this custom property
is set to 6.0.2.31, the remaining bridges recover
the high availability state of the failed bridge without the data
being unavailable in the local core group.
Complete
the following actions to set the IBM_CS_HAM_PROTOCOL_VERSION core
group custom property to 6.0.2.31 for all of
your core groups.
- Shut down all core group bridges in all of your core
groups.
- Repeat the following actions for each core group in
each of your cells:
- In the administrative console, click core_group_name >
Custom properties.
- Specify IBM_CS_HAM_PROTOCOL_VERSION in
the Name field, and 6.0.2.31 in
the Value field.
- Save your changes.
- Synchronize your changes across the topology.
- Restart all of the bridges in the topology.
All of the core groups within this topology are using
the 6.0.2.31 high availability manager protocol.
Example
In the cell_x cell, there are the x_core_group_1, x_core_group_2,
and x_core_group_3 core groups. Each core group already has
a core group access point. The following image illustrates an access
point group between the core groups in the cell_x cell and
an example of the configuration in the administrative console.
Figure 1. Three core group access points in the same cell belong to the
same access point group.

Perform the following
steps to configure communication between the three core groups in
the cell_x cell:
- Create the x_access_point_group access point
group. Add a core group access point to the access point group for
each core group that is in the cell. In this example, add the x_core_group_ap_1 , x_core_group_ap_2,
and x_core_group_ap_3 access points to the x_access_point_group access
point group.
- Create bridge interfaces for each core group access point. The
following diagram illustrates the bridge interfaces for thex_core_group_ap_2 core
group access point:
Figure 2. Core group access points contain one
or more bridge interfaces.
By creating an access point group and adding all core groups
in the cell to the access point group, you enabled communication between
all the core groups that are in the cell_x cell.