Use the following guidelines to help determine when to create a new high availability
group policy, and when to modify or delete an existing policy.
Do not delete the default IBM® provided policies
If you want to override one of the default
policies that IBM provides, it is recommended that you do not delete the current policy. Instead,
create a new policy with more specific match criteria. The policy with the greatest number of
matches is the one that is used. Not deleting the IBM provided policy enables you to revert back to
that policy if a problem occurs with your new policy.
Do not try to change the type of an existing policy
After a
policy for a high availability group is created, you can change some of the policy attributes such
as preferred servers, or failback, but you cannot change the policy type. If you need to change the
policy type, you must create a new policy and then use match criteria to associate it with the
appropriate high availability group. The High availability group policy selection
process topic describes how the high availability manager selects a policy for a high
availability group.
Do not change a policy associated with a high availability group
A component
does not necessarily support all policy types and options. Therefore, before changing the policy
that is associated with a given high availability group, make sure you fully understand if the
application server code using that high availability group supports the change. For example, if you
want to change the type of policy that is associated with the high availability group used by the
transaction manager component, make sure the transaction manager code supports the new policy type
before making the change.
Do not use the same match criteria for multiple policies in the same core
group
If you have multiple policies configured with identical match criteria, the policy
match to the associated high availability group is ambiguous. If you are creating a new policy to
replace an older policy that you created, you might need to delete the older policy to specify the
appropriate match criteria. Another alternative is to specify additional match criteria in each
policy so no ambiguity exists as to which policy is controlling the high availability
group.