Public Preview announcement - Azure DMS consistent snapshot without locks

[Guest Aditi_Gupta]

We’re pleased to announce that Azure DMS now provides preview support for consistent snapshot without locks, which businesses can use to migrate databases to Azure while those databases remain operational. MySQL Consistent Snapshot without locks is a new feature that allows users to take a Consistent Snapshot of a MySQL server without losing data integrity at source.

 

 

 

When you enable this option, a reconciliation phase will occur after the initial load. This is to ensure that the data written to your target is transactionally consistent with the source server from a specific position in the binary log.

 

 

 

With this feature, we don't take a read lock on the server. We instead read tables at different point in time, while keeping track of the different binlog positions of each table. This aids to reconcile the tables towards the end of the initial load by performing replication in catchup mode to get a consistent snapshot.

 

 

 

 

 

 

 

Key features of Consistent Snapshot without locks:

 

• Ability to support heavy workload servers or servers with long-running transactions without the need for read locks.
  
• Resilient in completing migrations even in the event of failures caused by transient network/server blips that result in loss of all the pre-created connections.
  
• Separate reconciliation phase to ensure data written to target server is transactionally consistent with the source server from a specific position in the binary log.
  

 

 

 

 

 

 

 

 

Known issues and limitations for Enable Consistent Snapshot without locks

 

• Tables with foreign keys having Cascade or Set Null on delete/on update clause aren't supported.
  
• No DDL changes should occur during initial load.
  

 

 

 

For more information about using Azure DMS consistent snapshot without locks, see the following documentation:

 

• https://learn.microsoft.com/en-us/azure/dms/migrate-azure-mysql-consistent-backup
  

 

If you have any feedback or questions about the information provided above, please leave a comment below or email us at AskAzureDBforMySQL@service.microsoft.com. Thank you!

 

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