Select Initial Data Synchronization Page (Always On Availability Group Wizards)

 

Updated: May 17, 2016

Applies To: SQL Server 2016

THIS TOPIC APPLIES TO: yesSQL Server (starting with 2016)noAzure SQL DatabasenoAzure SQL Data Warehouse noParallel Data Warehouse

Use the Always On Select Initial Data Synchronization page to indicate your preference for initial data synchronization of new secondary databases. This page is shared by three wizards—the New Availability Group Wizard, the Add Replica to Availability Group Wizard, and the Add Database to Availability Group Wizard.

The possible choices include Full, Join only, or Skip initial data synchronization. Before you select Full or Join only ensure that your environment meets the prerequisites.

In this topic:

  • Suspend log backup tasks for the primary databases during initial data synchronization.

  • For large database, full backup and restore operations can take extensive time and resources. In such cases, we recommend that you prepare secondary databases yourself. For more information, see To Prepare Secondary Databases Manually, later in this topic.

  • Full initial data synchronization requires you to specify a network share. Before you use a wizard to perform full initial data synchronization, we recommend that you implement a security plan for the access permissions on the network share folder. This precaution is important because potentially sensitive data in the backup file can be accessed by anyone who has a READ permission on the folder. Also, to protect your backup and restore operations, we recommend that you secure the network channels between every server instance that hosts an availability replica and the network share folder.

    If your backup and restore operations must be highly secured, we recommend that you select either the Join only or Skip initial data synchronization option.

For each primary database, the Full option performs several operations in one workflow: create a full and log backup of the primary database, create the corresponding secondary databases by restoring these backups on every server instance that is hosting a secondary replica, and join each secondary database to availability group.

Select this option only if your environment meets the following prerequisites for using full initial data synchronization, and you want the wizard to automatically start data synchronization.

Prerequisites for using full initial data synchronization

  • All the database-file paths must be identical on every server instance that hosts a replica for the availability group.

    System_CAPS_ICON_note.jpg Note


    If the backup and restore file paths differ between the server instance where you run the wizard and any server instance that is to host a secondary replica. The backup and restore operations must be performed manually using the WITH MOVE option. For more information, see To Prepare Secondary Databases Manually, later in this topic.

  • No primary database name can exist on any server instance that hosts a secondary replica. This means that none of the new secondary databases can exist yet.

  • You will need to specify a network share in order for the wizard to create and access backups. For the primary replica, the account used to start the Database Engine must have read and write file-system permissions on a network share. For secondary replicas, the account must have read permission on the network share.

    System_CAPS_ICON_important.jpg Important


    The log backups will be part of your log backup chain. Store the log backup files appropriately.

If prerequisites are not met

The wizard cannot create the secondary databases for this availability group. For information on how to prepare them, see To Prepare Secondary Databases Manually, later in this topic.

If prerequisites are met

If these prerequisites are all met and you want the wizard to perform full initial data synchronization, select the Full option and specify a network share. This will cause the wizard to create full database and log backups of every selected database and to place these backups on the network share that you specify. Then, on every server instance that hosts one of the new secondary replicas, the wizard will create the secondary databases by restoring backups using RESTORE WITH NORECOVERY. After creating each of the secondary databases, the wizard will join the new secondary database to the availability group. As soon as a secondary database is joined, data synchronizations starts on that database.

Specify a shared network location accessible by all replicas
To create and restore backups, the wizard requires that you specify a network share. The account used to start the Database Engine on each server instance that will host an availability replica must have read and write file-system permissions on the network share.

System_CAPS_ICON_important.jpg Important


The log backups will be part of your log backup chain. Store their backup files appropriately.

Select this option only if the new secondary databases already exist on each server instance that hosts a secondary replica for the availability group. For information about preparing secondary databases, see To Prepare Secondary Databases Manually, later in this section.

If you select Join only, the wizard will attempt to join each existing secondary database to the availability group.

Select this option if you want to perform your own database and log backups of every primary database, restore them to every server instance that hosts a secondary replica. After you exit the wizard, you will then need to join every secondary database on every secondary replica.

System_CAPS_ICON_note.jpg Note


For more information, see Start Data Movement on an Always On Secondary Database (SQL Server).

To prepare secondary databases independently of any Always On Availability Groups wizard, you can use either of the following approaches:

After creating a secondary database, apply all current log backups to the new secondary database.

Optionally, you can prepare all the secondary databases before you run the wizard. Then, on the wizard's Specify Initial Data Synchronization page, select Join only to automatically join your new secondary databases to the availability group.

Overview of Always On Availability Groups (SQL Server)

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