Oracle AI Database@Azure applies stricter hostname-prefix validation than the generic 63-character DNS-label maximum. For an Exadata VM Cluster, Oracle's DNS and network-design documentation specifies a maximum hostname-prefix length of 23 characters .

The value also has syntactic constraints. It must begin with a letter, end with an alphanumeric character, and can contain hyphens. Certain reserved values are prohibited. These restrictions exist because the supplied prefix becomes part of system-generated host and database-network names; Oracle must reserve additional character capacity for generated suffixes and service-specific naming constructs.

Therefore, 63 characters represents a general DNS-label ceiling but is not valid for this Exadata field. Thirty characters likewise exceeds the Oracle-specific limit, while 15 characters is unnecessarily restrictive.

The correct maximum is consequently 23 characters .

This is a configuration detail worth memorizing because hostname validation occurs during VM Cluster provisioning and an invalid prefix can block resource creation before the underlying Exadata compute nodes are deployed.

Study Guide reference: Configure Oracle AI Database@Azure Networking — Exadata VM Cluster DNS, hostname prefix rules and naming constraints.

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