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Memory-optimized system-versioned temporal table performance

  • Članek

Applies to: SQL Server 2016 (13.x) and later Azure SQL Database Azure SQL Managed Instance

This article discusses some specific performance considerations when using system-versioned memory-optimized temporal tables.

When you add system-versioning to an existing non-temporal table, expect a performance impact on update and delete operations, because the history table is updated automatically.

Performance considerations

Every update and delete is recorded in an internal memory-optimized history table. You might experience unexpected memory consumption if your workload uses those two operations massively. Therefore we advise you the following considerations:

  • Don't perform massive deletes from the current table in one step. Consider deleting data in multiple batches, with manually invoked data flush in between, with sp_xtp_flush_temporal_history, or while SYSTEM_VERSIONING = OFF.

  • Don't perform massive table updates at once, as it can result in memory consumption that is twice the amount of memory required to update a non-temporal memory-optimized table. This doubled memory consumption is temporary, because the data flush task works regularly to keep memory consumption of internal staging tables within projected boundaries in the steady state. The boundary is 10 percent of memory consumption of the current temporal table. Consider doing massive updates in multiple batches, or while SYSTEM_VERSIONING = OFF, such as using updates to set the defaults for newly added columns.

The period of activation for the data flush task isn't configurable, but you can manually execute sp_xtp_flush_temporal_history as needed.

Consider using clustered columnstore as a storage option for a disk-based history table, especially if you plan to run analytics queries on historical data that make use of aggregate or windowing functions. In that case, a clustered columnstore index is an optimal choice for your history table. Clustered columnstore indexes provide good data compression, and behave in an insert-friendly manner, aligning with how history data is generated.

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