Document the option to change backup memory settings via --additional-config (#2747)

Author: NataliaIvakina

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

@@ -275,17 +275,22 @@ This needs to be changed if backups are to be taken from another machine.
 [[online-backup-memory]]
 === Memory configuration
 
-The following options are available for configuring the memory allocated to the backup client:
-
-* Configure heap size for the backup::
+You can configure the memory allocated to the backup client in several ways:
 
+* Configure heap size:
++
 `HEAP_SIZE` configures the maximum heap size allocated for the backup process.
-This is done by setting the environment variable `HEAP_SIZE` before starting the operation.
+Define the variable `HEAP_SIZE` before starting the operation.
 If not specified, the Java Virtual Machine chooses a value based on the server resources.
 
-* Configure page cache for the backup::
+* Configure page cache:
++
+Set the page cache size with the `--pagecache` option of the `neo4j-admin database backup` command.
+
+* Override the memory settings:
++
+Use the `--additional-config` option of the `neo4j-admin database backup` command to override the memory configurations in the _neo4j.conf_ file.
 
-The page cache size can be configured by using the `--pagecache` option of the `neo4j-admin database backup` command.
 
 [TIP]
 ====