Step 3: Define the dynamic cluster members

You can define dynamic cluster members when you are creating a dynamic cluster, or you can add dynamic cluster members to an existing dynamic cluster.

To access this administrative console page, click Servers > Clusters > Dynamic clusters > New.

To add dynamic cluster members to an existing dynamic cluster, click Servers > Clusters > Dynamic clusters > dynamic_cluster_name > Dynamic cluster members > Add. You can only add dynamic cluster members to dynamic clusters that are in manual membership mode and do not have a membership policy defined.

Rule-based membership

You can use rule-based membership with application servers, WebSphere® Application Server Community Edition servers, or PHP servers.

Use the subexpression builder to build a Membership policy. The membership policy specifies which nodes are members of the dynamic cluster. Click Preview membership to view which nodes are in the dynamic cluster with the membership policy that you defined.

Example membership policies

To define membership as all nodes in a specific node group:
```
node_nodegroup = 'my_node_group'
```
To define membership as all nodes that run Apache:
```
node_property$APACHE_2_0 IS NOT NULL
```

To define membership as all nodes that run Apache and PHP:

node_property$APACHE IS NOT NULL and node_property$PHP IS NOT NULL

To define membership as all nodes that run WebSphere Application Server Community Edition Version 2.0 or later:
```
node_property$WASCE_2.0* IS NOT NULL
```
To define membership as all nodes that run WebSphere Application Server Community Edition Version 2.0 only:
```
node_property$WASCE_2.0 IS NOT NULL
```
To define membership as all nodes that have a name that is like my_node, including my_node_1, my_node_2, and so on:
```
node_name like 'my_node%'
```

To define membership as a list of specific host names:

node_hostname in ('node1.mydomain.com','node2.mydomain.com')

You can group subexpressions by using and, or, or not logical operators and parenthesis. The following example defines node membership as nodes that are not in the my_node_group node group, and have a name that is like my_node, including my_node_1, my_node_2, and so on.

not (node_nodegroup='my_node_group') and node_name like 'my_node%'

Manually defined membership

Use manually defined membership to add servers that exist in your configuration to the dynamic cluster.

For dynamic clusters that have application servers, you use an existing static cluster. Select an existing static cluster from the list to use.
For servers with assisted life cycle management, select the servers that you want to add to the dynamic cluster. Click Add member. The servers that are added to your dynamic cluster display in the list. To create a new dynamic cluster member, click Add. To remove a member, click Remove. The dynamic cluster must have members that are all of the same server type.

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