Explain the use of prefer-diff-as-parent

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

@@ -161,7 +161,7 @@ Note: this is an EXPERIMENTAL option. Consult Neo4j support before use.
 |false
 
 |--prefer-diff-as-parent
-|label:new[Introduced in 2025.04] When performing a differential backup, prefer the latest non-empty differential backup as the parent instead of the latest full backup.
+|label:new[Introduced in 2025.04] When performing a differential backup, prefer the latest non-empty differential backup as the parent instead of the latest backup.
 |false
 
 |--temp-path=<path>
@@ -459,3 +459,207 @@ bin/neo4j-admin database backup --to-path=azb://myStorageAccount/myContainer/myD
 ----
 ======
 =====
+
+
+[role=label--new-2025.04]
+[[diff-backup-as-parent]]
+=== Perform a differential backup using the `--prefer-diff-as-parent` option
+
+When taking a differential backup with the `--type=DIFF` option, the parent, by default, is the *most recent non-empty* backup in the directory.
+In some cases, you may prefer to use the *latest differential* backup as the parent, even if there is a more recent full backup.
+You can do this by setting the option `--prefer-diff-as-parent` to `True`.
+
+This can be used to ensure you have differential backups for all transactions, which would allow you to restore to any point in time.
+Otherwise, the transactions between a full backup and the previous differential backup will not be backed up as individual transactions.
+
+The examples below cover different scenarios for using the `--prefer-diff-as-parent` option.
+
+[.tabbed-example]
+=====
+[role=include-with-Chain-with-full-and-differential-backups]
+======
+
+Let's assume that every hour you write 10 transactions to the `neo4j` database, except from 12:30-13:30, when you do not write any transaction.
+
+There is a backup job that takes a backup every hour and a full backup every four hours.
+We refer as an _empty_ backup a backup that has no transactions, meaning that both the lower transaction ID and the upper transaction ID are zero.
+
+Imagine you have the following backup chain:
+
+[cols="h,e,m,h,h"]
+|===
+|Timestamp | Backup name | Backup type | Lower Transaction ID | Upper Transaction ID
+
+| 10:30
+| backup1
+| FULL
+| 1
+| 10
+
+| 11:30
+| backup2
+| DIFF
+| 11
+| 20
+
+| 12:30
+| backup3
+| DIFF
+| 21
+| 30
+
+| 13:30
+| backup4
+| DIFF
+| 0
+| 0
+
+| 14:30
+| backup5
+| FULL
+| 1
+| 40
+
+|===
+
+At 15:30, you execute the following backup command:
+
+[source,shell]
+----
+neo4j-admin database backup --from=<address:port> --to-path=<targetPath> --type=DIFF neo4j
+----
+
+The result would be:
+
+[cols="h,e,m,h,h"]
+|===
+| 14:30
+| backup6
+| DIFF
+| 41
+| 50
+|===
+
+The result means you have chosen `backup5` as the parent for your differential `backup6` since the `backup5` is the *latest non-empty* backup.
+
+However, if you execute the following command with the `--prefer-diff-as-parent` option:
+
+[source,shell]
+----
+neo4j-admin database backup --from=<address:port> --to-path=<targetPath> --type=DIFF --prefer-diff-as-parent neo4j
+----
+
+The result would be:
+
+[cols="h,e,m,h,h"]
+|===
+| 14:30
+| backup6
+| DIFF
+| 31
+| 50
+|===
+
+In this case, the `backup3` is selected as the parent since it is the *latest non-empty differential* backup.
+
+======
+[role=include-with-Chain-with-only-full-backups]
+======
+
+Let's assume that you write 10 transactions to the `neo4j` database every hour and trigger an hourly full backup.
+
+[cols="h,e,m,h,h"]
+|===
+|Timestamp | Backup name | Backup type | Lower Transaction ID | Upper Transaction ID
+
+| 10:30
+| backup1
+| FULL
+| 1
+| 10
+
+| 11:30
+| backup2
+| FULL
+| 11
+| 20
+|===
+
+In this case, there is no differential backup.
+Therefore, the `--prefer-diff-as-parent` option has no effect and the behaviour is the same as the default one.
+
+[source,shell]
+----
+neo4j-admin database backup \
+--from=<address:port> --to-path=<targetPath> \
+--type=DIFF --prefer-diff-as-parent \
+neo4j
+----
+
+The result would be (with or without the `--prefer-diff-as-parent` option):
+[cols="h,e,m,h,h"]
+|===
+| 12:30
+| backup3
+| DIFF
+| 21
+| 30
+|===
+
+======
+[role=include-with-Chain-with-only-empty-full-backups]
+======
+
+Let's assume that the database is empty and you do not write anything to it, while still taking hourly full backups.
+
+[cols="h,e,m,h,h"]
+|===
+|Timestamp | Backup name | Backup type | Lower Transaction ID | Upper Transaction ID
+
+| 10:30
+| backup1
+| FULL
+| 0
+| 0
+
+| 11:30
+| backup2
+| FULL
+| 0
+| 0
+|===
+
+In this case, you cannot perform a differential backup with the `--type=DIFF` option, and the below command fails anyway, whether you used the `--prefer-diff-as-parent` or not.
+This occurs because we are looking for the *latest non-empty* backup, and there are only empty backups.
+
+[source,shell]
+----
+neo4j-admin database backup \
+--from=<address:port> --to-path=<targetPath> \
+--type=DIFF --prefer-diff-as-parent \
+neo4j
+----
+
+But if you select the `--type=AUTO` option, the command will succeed, and the result would be another empty *full* backup.
+
+[source,shell]
+----
+neo4j-admin database backup \
+--from=<address:port> --to-path=<targetPath> \
+--type=AUTO --prefer-diff-as-parent \
+neo4j
+----
+
+The result would be:
+
+[cols="h,e,m,h,h"]
+|===
+| 12:30
+| backup3
+| FULL
+| 0
+| 0
+|===
+
+======
+=====