Serialization-The Authority attribute

VCS ensures that multi-cluster service group operations are conducted serially to avoid timing problems and to ensure smooth performance. The Authority attribute prevents a service group from coming online in multiple clusters at the same time. Authority is a persistent service group attribute and it designates which cluster has the right to bring a global service group online. The attribute cannot be modified at runtime.

If two administrators simultaneously try to bring a service group online in a two-cluster global group, one command is honored, and the other is rejected based on the value of the Authority attribute.

The attribute prevents bringing a service group online in a cluster that does not have the authority to do so. If the cluster holding authority is down, you can enforce a takeover by using the command hagrp -online -force service_group. This command enables you to fail over an application to another cluster when a disaster occurs.

Note   A cluster assuming authority for a group does not guarantee the group will be brought online on the cluster. The attribute merely specifies the right to attempt bringing the service group online in the cluster. The presence of Authority does not override group settings like frozen, autodisabled, non-probed, and so on, that prevent service groups from going online.

You must seed authority if it is not held on any cluster.

Offline operations on global groups can originate from any cluster and do not require a change of authority to do so, because taking a group offline does not necessarily indicate an intention to perform a cross-cluster failover.

Authority and AutoStart

The attributes Authority and AutoStart work together to avoid potential concurrency violations in multi-cluster configurations.

If the AutoStartList attribute is set, and if a group's Authority attribute is set to 1, the VCS engine waits for the wac process to connect to the peer. If the connection fails, it means the peer is down and the AutoStart process proceeds. If the connection succeeds, HAD waits for the remote snapshot. If the peer is holding the authority for the group and the remote group is online (because of takeover), the local cluster does not bring the group online and relinquishes authority.

If the Authority attribute is set to 0, AutoStart is not invoked.