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. See
High availability group policy selection process for
a description of how the high availability manager selects a policy for a
high availability group.
Make sure that you know which policies a component using that
high availability group supports before creating a new policy to associate
with that 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.