Every high availability group has to have an associated policy.
This policy determines which members of a high availability group to put
in the active state.
Before you begin
Before creating a new policy, you should review the following topics:
You should also know:
- The name of the core group that you want to associate with the new policy.
- The name of the high availability group that you want this policy to control.
- The function, such as transaction log recovery or messaging engine, that
is associated with this high availability group.
- The policy types, such as One of N or Static, that this function supports.
- The type of policy you want to create.
- The policy settings, such as failback, and preferred servers only, that
you want to configure for this policy.
About this task
WebSphere Application Server includes default policies that are already
associated with the high availability groups some of the WebSphere Application
Server components use. If these default policies do not meet the requirements
of your installation, it is recommended that you create a new policy instead
of changing one of the default policies. The creation of new policies provides
you with the capability to tailor the policy settings to your installations
requirements while giving you the option to revert back to the default policy.
To
create a new policy:
Procedure
- In the administrative console, click Servers > Core groups >
Core group settings core_group_name > Policies > New.
- Select the new policy you want in effect for a specific high availability
group. If you need to define a new policy, the policy options are:
- All active policy: All of the group members are activated.
- M of N policy: M group members are activated. The number that is
represented by M is defined as part of the policy details.
- No operation policy: No group members are activated.
- One of N policy: Only one group member is activated.
- Static policy: The active members of a group are statically configured.
- Click Next.
- Specify a name for the policy in the Name field. The name must
be unique within the scope of the core group. Make the name meaningful
to other administrators.
- Optional: Specify a Description of the policy in the
description field. This description might include the name of the
associated core group.
- Specify a value for the Is alive timer field, if the default value
is too long or too short a time period. This value determines how
frequently the high availability manager checks the health of the high availability
group members. The default value is 0 seconds.
- If you specify -1 (minus 1), the Is alive timer is
disabled.
- If you specify 0 (zero), the value that is specified
for the Is alive timer at the core group services level is used for high availability
groups that are associated with this policy.
- If you specify an integer between 1 and 2147483647, inclusive, this value
is used for the high availability groups that are associated with this policy.
- Make sure the Quorum field is not selected. You should
not enable Quorum unless you are explicitly instructed to do so in the documentation
for some other product.
- Select the Failback field if you want to have the high availability
manager make the most preferred member the currently active member whenever
this action is possible. This option is available only for M of
N and One of N policies.
- Select the Preferred servers only field if you want the
high availability manager to only activate group members on servers that are
contained in the Preferred servers list. This option is available
only for M of N and One of N policies. If you select this option, you must
configure a list of preferred servers. A description of how to set up this
list is provided in a later optional step.
- Specify the number of group members that you want active in the
Number of active members field. This option is available only for
an M of N policy.
- Click Apply and then select Match criteria.
- On the next panel, click New and then configure the match
criterion for this policy.
- In the Name field, specify the name of one of the name-value
pairs contained in the name of the high availability group that you want to
associate with this policy.
- In the Value field, specify the value of the name-value pair
you specified in the Name field.
- Optional: In the Description field, add a description
of this match criterion . For example, you might specify First
attribute to indicate that this name-value pair matches the first
attribute contained in the group name.
- Click OK.
- Repeat these steps for each additional attribute you want to
include as part of your match criterion.
You should set the match criterion for a new policy to two or more of
the name-value attributes that are contained in the name of the high availability
group to ensure that this policy is used instead of one of the WebSphere Application
Server default policies. Using this example, the following
high availability group-to-policy association is established:
- Uunder Additional Properties, select the Static group
servers field to configure the list of servers that you want activated.
This option is available only for Static policies. Click Add to
move core group servers into the list of Static group servers, and then Click OK after
you complete the list.
- Optional: Under Additional Properties, select Preferred
servers and select the preferred servers for this policy. This
option is available only if you selected the Preferred servers only field
for M of N and One of N policies. If you do not set up this list, no group
members are activated.
Click Add to move core group servers into
the list of preferred servers.
Select specific servers in the list
and click Move up and Move down to adjust the order of the servers
within the list. Make sure that the most preferred server is at the beginning
of the list and the least preferred server is at the end of the list.
After
you complete the preferred servers list, click OK.
Important: Use
caution when selecting preferred servers. WebSphere Application Sever cannot
detect if you select an inappropriate server as a preferred server. For example,
if the policy affects a messaging engine or transaction service, only select
preferred servers from the messaging engine cluster. Similarly, if the policy
affects a transaction service, only select preferred servers from the transaction
service cluster.
- Click OK, and then click Save to
save your changes.
- Select Synchronize changes with nodes,
and then click Save again.
Results
The new policy goes into affect after it is saved and synchronized.
You do not have to stop and restart the affected application servers.
What to do next
You can change the
Failback and
Preferred servers only options
for this policy without stopping and restarting the affected application
servers.
You can create or update the list of preferred servers that for
this policy without stopping and restarting the affected application servers.