High availability group policy modification guidelines

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

To override one of the default policies that IBM provides, IBM recommends that we 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 used. Not deleting the IBM provided policy enables us to revert back to that policy if a problem occurs with the new policy.

Do not try to change the type of an existing policy

After a policy for a high availability group is created, we can change some of the policy attributes such as preferred servers, or failback, but we cannot change the policy type. To change the policy type, 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 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, to change the type of policy 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 we have multiple policies configured with identical match criteria, the policy match to the associated high availability group is ambiguous. For a new policy to replace an older policy that we created, we 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.

Related:

High availability group policy selection process