'Failed to restore backup: Incompatible version' error during SonarQube major version restore

Error context

Restoring a SonarQube 9.9 backup to a 10.x instance fails with the logged message Failed to restore backup: Incompatible version in web.log during the database migration step. The backup ZIP contains a database dump and configuration files but excludes Elasticsearch indices, which are rebuilt on startup.

Goal and constraints

The objective is to define the exact version compatibility rules for backup restoration and establish reliable verification that recovered data — including Elasticsearch indexes — is complete and consistent. Constraints include: the restore process requires the same major version; Elasticsearch rebuild can take hours and may fail silently if heap size is insufficient; no built‑in checksum or integrity check exists for the backup file; and backups taken on active instances may capture partial data causing foreign‑key violations.

Open questions

1. Does the "Incompatible version" error strictly enforce major version equality, or are there documented minor version tolerances for backup restoration?
2. What programmatic verification methods exist to confirm Elasticsearch index rebuild completion beyond monitoring web.log for the completion message?
3. Can the built‑in backup be used to migrate data across major versions when combined with database‑native tools, or is a fresh installation with manual data migration the only supported path?