Database migration methods

migration-logo-2389341When thinking about migration the most common issue is downtime. There are some methods that require downtime like backup/restore or less downtime using Log Shipping.

You can choose several different methods to migrate your database.  For example, methods that require downtime include:

  • Backup the database, manually copy the backup file to the machine and then restore the database there. This method is simple and the use of compression minimizes the time that is required.
  • Perform a backup to an Azure Blob storage account, and then restore the database from that backup. This method removes the necessity to manually copy the backup file.
  • Detach the database, copy the files to an Azure Blob storage and then attach them to the SQL Server instance. Use this method if you plan to store database files in Azure Blob storage permanently instead of on a hard disk.
  • Log Shipping, use a backup/restore process and the downtime depends on the transaction log file backup copying a small file in the process. This method is simple and is necessary a connection between the machines and permission to copy the backup files.

Methods that not require downtime:

  • AlwaysOn, adding a new secondary replica after replication has completed, you can failover to make the machine the primary replica. For Azure virtual machine use the Add Azure Replica Wizard.
  • Transactional Replication will minimize downtime, but don’t have an AlwaysOn deployment in your SQL Server system.

If you need help to decide which method is better for your scenario, feel free to contact me.

SqlPackage a tool to import/export SQL Server and Azure SQL DB

repair_database-512SqlPackage is a command-line utility that you can use for exporting and importing operations in both on-premises SQL Server databases and in cloud databases. SqlPackage supports the following operations:

  • Extract. Creates a database snapshot DACPAC file from a SQL Server database or from Azure SQL Database.
  • Publish. Updates the schema in a live database to match the schema in a DACPAC
    file. If the database does not exist on the destination server, the publish operation
    creates it.
  • Export. Exports both schema and data from a SQL Server database or from Azure SQL Database into a BACPAC file.
  • Import. Imports the schema and data from a BACPAC into a new database.
  • DeployReport. Creates an XML report that describes the changes that would be made by a publish operation.
  • DriftReport. Creates an XML report of the changes that have been made to a registered database.
  • Script. Creates a Transact-SQL script that you can use to update the schema of a target database to match the schema of a source database.
    Use the /Action: or /a parameter to specify which action to execute.

SqlPackage example to import from bacpac file to Azure
sqlpackage.exe /Action:Import /tsn:tcp:.database.windows.net,1433 /tdn: /tu: /tp: /sf: /p:DatabaseEdition=Premium /p:DatabaseServiceObjective=P4 /p:Storage=File

More about SqlPackage parameters:
https://msdn.microsoft.com/en-us/library/hh550080%28v=vs.103%29.aspx?f=255&MSPPError=-2147217396

What is Stretch Database?

Stretch Database is a feature of SQL Server where data can be split between on-premises storage and cloud storage. With Stretch Database, cold, historical data is kept in the cloud and active data is kept on-premises for maximum performance.

Stretch Database requires no changes to client applications or existing Transact-SQL queries, so you can implement it seamlessly for existing applications. Stretch Database can reduce on-premises storage requirements both for data and associated backups. Backups of on-premises data are smaller and therefore run quicker than standard backups. Data in the cloud is backed up automatically.

With Stretch Database, cold historic data remains available for users to query, although there might be a small amount of additional latency associated with queries.

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Implement a Stretch Database
You can implement Stretch Database entirely within SQL Server Management Studio; you do not need to pre-configure servers or storage within Microsoft Azure.
Implementing Stretch Database involves the following steps:

  1. Start Microsoft SQL Server Management Studio and connect to the instance of SQL Server.
  2. In Object Explorer, expand Databases.
  3. Right-click the database, point to Tasks, point to Stretch, and then click Enable.

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scretch3scretch4scretch5Complete the steps in the Enable Database for Stretch wizard to create a  Database Master Key; identify the appropriate tables and configure the Microsoft Azure deployment.

After implementing Stretch Database, you can monitor it from SQL Server  Management Studio.

In Object Explorer, expand Databases, right-click the stretch-enabled database, point to Tasks, point to Stretch, and then click Monitor to open the Stretch Database Monitor. This monitor shows information about both the local and Azure SQL instances, along with data migration status.