Tuesday, March 22, 2022

Backup Anywhere offers Expanded Replication for High Availability and More Flexibility


Backup Anywhere offers Expanded Replication for High Availability and More Flexibility

The previous release of the Zero Data Loss Recovery Appliance software ( includes 3 new exciting features for replication. 

  • Backup Anywhere - Providing the ability to change roles (upstream vs downstream).
  • Read Only replication - Providing seamless migration to a different Recovery Appliance.
  • Request Only Replication - Providing a High Availability option for backups.

Backup Anywhere

 Backup Anywhere provides even more options for HADR (High Available/Disaster Recovery) with the ability to redirect backups and redo to another Recovery Appliance. In addition, Backup Anywhere provides the ability to perform a role reversal, removing the concept of upstream/downstream.  As the name implies, when replicating between two or more Zero Data Loss Recovery Appliances you can switch the Recovery Appliance that is receiving backups from your protected databases. 

With Backup Anywhere you configure two Recovery Appliance as pairs and create replication servers that point to each other.  The metadata synchronization will ensure backups are replicated to its pair and ensures the Replication Appliance pairs stay in sync.

NOTE: In order to use Backup Anywhere you must use the new REPUSER naming convention of REPUSER_FROM_<source>_TO_<destination>.

For my example, the diagram below depicts a three Zero Data Loss Appliance architecture with the primary databases in New York sending backups to the Recovery Appliance in the New York Data Center,  The Recovery Appliance in the New York Data Center replicates backups to the Recovery Appliance in the London Data Center. And finally, the Recovery Appliance in the London Data Center replicates backups to the Recovery Appliance in Singapore.

New York --> London --> Singapore

But what happens If I want to change which Recovery Appliance I am sending my backups to? With Backup Anywhere I can change the Recovery Appliance receiving backups, and the flow of replicated backups will be taken care of automatically.  With Backup Anywhere the Recover Appliances will seamlessly change the direction of the replication stream based on which Recover Appliance is currently receiving the backups.  Backup Anywhere does this automatically and will still ensure backups on the three Zero Data Loss Appliances are synchronized and available

Singapore --> London --> New York.


Read Only Replication

This is my favorite new feature included in the latest Recovery Appliance release. Read Only allows you to easily migrate your backups to a new Recovery Appliance while leaving the older backups still available.

Replication normally synchronizes the upstream catalog with the downstream catalog AND ensures that backups are replicated to the downstream. With Read Only Replication, only the synchronization occurs.  The upstream Recovery Appliance (typically the new RA) knows about the backups on the downstream Recovery Appliance (the old RA).  If a restore is requested that is not on the upstream Recovery Appliance, the upstream will pull the backup from the downstream.

The most common use case is retiring older pieces of equipment, but Read Only Replication can be used for additional use cases.

  • Migrating backups to a new datacenter
  • Migrating backups for a subset of database from an overloaded Recovery Appliance to a new Recovery Appliance to balance the workload

 Replace older Recovery Appliance

In this example I want to replace the current Recovery Appliance (ZDLRAOLD) with a new Recovery Appliance (ZDLRANEW).  During this transition period I want ensure that backups are always available from the protected database.  This example will show the migration of backups from ZDLRAOLD to ZDLRANEW. I am keeping 30 days of backups for my databases and I am starting the migration on September 1.

Step #1 - September 1, configure replication from ZDLRAOLD to ZDLRANEW

Create a replication server from ZDLRAOLD to ZDLRANEW and add the policy(s) for the databases to the replication server.  This will replicate the most current level 0 backup (FULL)  onto ZDLRANEW for all databases without changing the backup location from the protected databases.

Once you have ensured that all databases have replicated a level 0 backup to ZDLRANEW you can remove the replication server from ZDLRAOLD which will stop the replication.

Step #2 - September 2, configure Read Only replication from ZDLRANEW to ZDLRAOLD

Create a replication server from ZDLRANEW to ZDLRAOLD. Add the policies all databases to the replication server and ensure that the read only flag is set when adding the policy.


PROCEDURE add_replication_server (
   replication_server_name IN VARCHAR2,
   protection_policy_name IN VARCHAR2
   skip_initial_replication IN BOOLEAN DEFAULT FALSE,
   request_only IN BOOLEAN DEFAULT FALSE);

Note: The Read Only flag must be set when adding the policy to the replication server to ensure backups are NOT replicated from ZDLRANEW to ZDLRAOLD.



Step #3 - September 3, configure backups from the protected databases to backup to ZDLRANEW.

At this point ZDLRANEW should contain at least 1 full backup for all databases, and the incremental backups will begin on September 3rd.  ZDLRANEW will now contain backups from September 1 (when replication began) until the most current Level 0 virtualized backup taken.  ZDLRAOLD will contain backups from August 4 until September 2nd when protected database backups to ZDLRAOLD were moved to be sent to ZDLRANEW.

Step #4 - September 4+, ZDLRANEW contains all new backups and old backups age off ZDLRAOLD

Below is a snapshot of what the backups would look like 15 days later on September 15th.  Backups are aging off of ZDLRAOLD and ZDLRANEW now contains 15 days of backups.


Step #5 - September 15, Restore backups

To restore the protected database using a point in time you would connect the protected database to ZDLRANEW and ZDLRANEW would provide the correct virtual full backup regardless of its location.

1.       If the Full backup prior to the point-in-time is on ZDLRANEW it is restored directly from there.

2.     If the Full backup is NOT on ZDLRANEW, it will get pulled from ZDLRAOLD through ZDLRANEW back to the protected database

The location of the backups is transparent to the protected database, and ZDLRANEW manages where to restore the backup from.

Step #6 - September 30  Retire ZDLRAOLD

At this point the new Recovery Appliance ZDLRANEW contains 30 days of backups and the old Recovery Appliance ZDLRAOLD can be retired.


Request Only Mode


Request Only Mode is used when Data Guard is present and both the Primary database and the Data Guard database are backing up to a local Recovery Appliance. The two Recovery Appliances synchronize only  the metadata, no backup pieces are actively replicated. But, in the event of a prolonged outage of either Recovery Appliance, this features provides the ability to fill gaps by replicating backups from its paired Recovery Appliance. 

To implement this feature, replication servers are configured on both Recovery Appliances, and the policies are added to the replication server specifying REQUEST_ONLY=TRUE.


PROCEDURE add_replication_server (
   replication_server_name IN VARCHAR2,
   protection_policy_name IN VARCHAR2
   skip_initial_replication IN BOOLEAN DEFAULT FALSE,
   request_only IN BOOLEAN DEFAULT FALSE);

Below is my environment that is configured and running in a normal mode. I have my primary database in San Francisco, and my standby database in New York.  Both databases, Primary and Standby are backing up to the local Recovery Appliance in their respective same data center.  Request Only Mode is configured between the two Recovery Appliances.


To demonstrate what happens when a failure occurs, I will assume that the Recovery Appliance in the SFO datacenter is down for a period of time.  In this scenario, backups can no longer be sent to the SFO Recovery Appliance, but Data Guard Redo Traffic still occurs to the standby database in New York, and the standby database in New York is still backing up locally to the Recovery Appliance in New York.

When the SFO appliance comes back on-line, it will synchronize the backup information with that on the NYC Recovery Appliance.  The SFO appliance will request datafile backups and any controlfile backups that are older than 48 hours, from NYC appliance.

NOTE: The assumption is that a new backup will occur locally over a faster LAN network and fill any gaps within the last 48 hours. The backups requested from its pair will be transferred over a slower WAN and fill any gaps older than 48 hours

If Real-Time redo is configured, the protected databases will immediately begin the archived log gap fetch process, and fill any gaps in archive logs on SFO appliance that are available on the protected databases. The SFO appliance will also check for new logs to be requested from NYC appliance once per hour over the next 6 hours. This gives time for local arch log gap fetch to run via LAN, which is faster than replicating logs via WAN from NYC.

HADR Bonus Feature: Since the SFO appliance recovery catalog is immediately synchronized with the NYC recovery catalog, backup pieces on the NYC Recovery Appliance are available for recovery.  With this capability you have full recovery protection as soon as the catalog synchronization completes.




This ensures that the SFO Recovery Appliance will be able to provide a short Recovery Point Object without waiting for the next backup job to occur.

All of this happens transparently and quickly returns the Recovery Appliance to the expected level of protection for the database backups.


For more details on implementing different replication modes, refer to the Administrator’s Guide.