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Chapter 2Introduction to the Properties of a NodeThis chapter introduces the roles, qualification levels and attributes of nodes. For information about the types of nodes, see the Netra High Availability Suite Foundation Services 2.1 6/03 Overview. Membership RolesPeer nodes can be recognized by the CMM API as having the following membership roles: No membership role is assigned to a node running the Foundation Services services and fully participating in cluster communication that is neither a master node nor a vice-master node. Further information about nodes in the cluster is provided by the cluster_nodes_table(4) man page. For information about the definitions of the roles of nodes in the cluster, see "Cluster Model" in the Netra High Availability Suite Foundation Services 2.1 6/03 Overview. Membership roles are dynamic and are defined by the master node. Unless the membership role of a node is CMM_OUT_OF_CLUSTER, the node is by default viewed as being in the cluster. While the node has the CMM_OUT_OF_CLUSTER role, the qualification level and CMM_FLAG_SYNCHRO_NEEDED flag are meaningless. Information about the membership role of a node can be found in the sflag field of the cmm_member_t structure. See Using the sflag Field of the cmm_member_t Structure. Qualification LevelsThe qualification level of a node is applicable only to master-eligible nodes. On these nodes, the qualification level determines whether the node can participate in an election for the master role or vice-master role. A master-eligible node can be qualified or disqualified. The qualification levels of a master-eligible node are:
For master-eligible nodes, the qualification level is stored in the minimum configuration file, target.conf, on the node and in the cluster node table. For more information, see the target.conf(4) man page. The qualification level is persistent, that is, if the node is rebooted, the node starts with the same qualification level it had before the reboot. The qualification level of a node can be changed during runtime. Diskless and dataless nodes are never assigned qualification levels. To assign a new qualification level to a node, use the cmm_member_setqualif function. For more information, see the cmm_member_setqualif(3CMM) man page. An example in which this function is used to trigger a failover in the cluster is provided in this book. See Triggering a Failover by Using the cmm_member_setqualif()Function. Administrative AttributesThe CMM API recognizes each node in the cluster as having an administrative attribute. An attribute can be any of the following:
A master node can be demoted because of a change in its administrative attributes, when the vice-master detects a problem on the master, or after a call to the cmm_mastership_release() function. The master node can also be demoted in the case of a failover. See Failover Notifications. A node assumes the master role if it is sufficiently qualified. Information about the administrative attributes of a node can be found in the sflag field of the cmm_member_t structure. For more information, see Using the sflag Field of the cmm_member_t Structure. | ||||
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