Edit

Azure Synapse Link for Azure SQL Database

  • Article

This article helps you to understand the functions of Azure Synapse Link for Azure SQL Database. You can use the Azure Synapse Link for SQL functionality to replicate your operational data into an Azure Synapse Analytics dedicated SQL pool from Azure SQL Database.

A link connection identifies a mapping relationship between an Azure SQL database and an Azure Synapse Analytics dedicated SQL pool. You can create, manage, monitor and delete link connections in your Synapse workspace. When creating a link connection, you can select both source database and a destination Synapse dedicated SQL pool so that the operational data from your source database will be automatically replicated to the specified destination Synapse dedicated SQL pool. You can also add or remove one or more tables from your source database to be replicated.

You can start, stop, pause or resume a link connection. When started, a link connection will start from a full initial load from your source database followed by incremental change feeds via the change feed feature in Azure SQL database. When you stop a link connection, the updates made to the operational data won't be synchronized to your Synapse dedicated SQL pool. It will do a full initial load from your source database if you start the link connection again. When you pause a link connection, the updates made to the operational data won't be synchronized to your Synapse dedicated SQL pool. When you resume a link connection, it will continue to synchronize the update from the place where you paused the link connection to your Synapse dedicated SQL pool. For more information, see Azure Synapse Link change feed for SQL Server 2022 and Azure SQL Database.

You need to select compute core counts for each link connection to replicate your data. The core counts represent the compute power and it impacts your data replication latency and cost.

You also have the chance to make a trade-off between cost and latency by selecting the continuous or batch mode to replicate the data. When you select continuous mode, the runtime will be running continuously so that any changes applied to your SQL DB or SQL Server will be replicated to Synapse with low latency. When you select batch mode with specified interval, the changes applied to your SQL DB or SQL Server will be accumulated and replicated to Synapse in a batch mode with specified interval. By doing so, you can save cost as you are only charged for the time when the runtime is required to replicate your data. After each batch of data is replicated, the runtime will be shut down automatically.

Monitoring

You can monitor Azure Synapse Link for SQL at the link and table levels. For each link connection, you'll see the following status:

  • Initial: a link connection is created but not started. You will not be charged in initial state.
  • Starting: a link connection is setting up compute engines to replicate data.
  • Running: a link connection is replicating data.
  • Stopping: a link connection is going to be stopped. The compute engine is being shut down.
  • Stopped: a link connection is stopped. You will not be charged in stopped state.
  • Pausing: a link connection is going to be paused. The compute engine is being shut down.
  • Paused: a link connection is paused. You will not be charged in paused state.
  • Resuming: a link connection is going to be resumed by setting up compute engines to continue to replicate the changes.

For each table, you'll see the following status:

  • Snapshotting: a source table is initially loaded to the destination with full snapshot.
  • Replicating: any updates on source table are replicated to the destination.
  • Failed: the data on source table can't be replicated to destination due to a fatal error. If you want to retry after fixing the error, remove the table from link connection and add it back.
  • Suspended: replication is suspended for this table due to an error. It will be resumed after the error is resolved.

You can also get the following metrics to enable advanced monitoring of the service:

  • Link connection events: number of link connection events including start, stop or failure.
  • Link table event: number of link table events including snapshot, removal or failure.
  • Link latency in second: data processing latency in second.
  • Link data processed data volume (bytes): data volume in bytes processed by Synapse link for SQL.
  • Link processed row: row counts (changed) processed by Synapse Link for SQL.

For more information, see Manage Synapse Link for SQL change feed.

Transactional consistency across tables

You can enable transactional consistency across tables for each link connection. However, it limits overall replication throughput.

Known limitations

A consolidated list of known limitations and issues can be found at Known limitations and issues with Azure Synapse Link for SQL.

Next steps