Explain the use of prefer-diff-as-parent

Author: NataliaIvakina

modules/ROOT/pages/backup-restore/online-backup.adoc

@@ -459,3 +459,17 @@ bin/neo4j-admin database backup --to-path=azb://myStorageAccount/myContainer/myD
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+[role=label--new-2025.04]
+[[diff-backup-as-parent]]
+=== Perform a differential backup using the `--prefer-diff-as-parent` option
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+When creating a differential backup, the parent is always the most recent (non-empty) backup in the directory.
+In some cases the directory may have two equally recent backups -- a full backup and a differential one.
+By default, the full backup is chosen as the parent.
+But you can use the differential backup as the parent by setting the option `--prefer-diff-as-parent` to `True`.
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