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Table of Contents
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What is a Group Change?

ClustrixDB Xpand uses a distributed group membership protocol to maintain the static set of all nodes known to the cluster and checks that the nodes maintain active communication between each other. Clustrix Xpand refers to this as a Group.

When the set of nodes changes, there is a change in the group and a Group Change occurs. During a Group Change, ClustrixDB Xpand performs tasks to ensure:

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What Happens During a Group Change?

If ClustrixDB Xpand detects a change in its group, it will recover automatically as long as a quorum of nodes is available. Your cluster will experience a brief period during which transactions are suspended while the group is being reformed and the consistency of the database is ensured. Connections from applications to surviving nodes will remain but transactions and queries for those connections will be temporarily paused. 

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When there is a Group Change, the cluster pauses all processing and determines whether a quorum of nodes is available. If true, ClustrixDB Xpand performs a series of internal operations in preparation for the new group. Together these operations may take a few seconds, or 10s or seconds, depending on how large the cluster is, how large the database is, and how many transactions were in-process when the Group Change occurred. These steps ensure that the consistency of the database is guaranteed despite having lost a member of the cluster.

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