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Transaction log file grows for databases with In-Memory OLTP in SQL Server 2022

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Symptoms

When your databases have the In-Memory OLTP feature enabled in SQL Server 2022, you notice the transaction log file grows continuously. In addition, the SQL Server error log might have messages like Close thread is falling behind: 4 checkpoints outstanding.

If you restart the SQL Server instance, you might notice the database takes a long time to complete the database recovery process.

Troubleshoot the issue with sys.databases and sys.dm_db_xtp_checkpoint_stats

  • When you use the catalog view sys.databases to gather information and troubleshoot this issue, the column log_reuse_wait_desc shows XTP_CHECKPOINT as the reason for long truncation. This value indicates that the transaction log is waiting for an In-Memory OLTP (formerly known as Hekaton) checkpoint to occur. It suggests a delay in checkpointing operations, potentially impacting performance or log file growth.

  • When you use the SQL Server dynamic management view (DMV) sys.dm_db_xtp_checkpoint_stats to gather information and troubleshoot this issue, the column outstanding_checkpoint_count shows a nonzero value for an extended period of time. It indicates that checkpoints aren't occurring efficiently, potentially affecting performance and log file growth.

Cause

SQL Server 2022 introduced new capabilities that improve memory management in large memory servers to reduce out-of-memory conditions. A known issue in this change can sometimes lead to the behavior described in the Symptoms section.

Resolution

To solve the issue, follow these steps:

  1. Add -T9810 as the startup parameter for the SQL Server instance.
  2. Restart the instance.
  3. Issue a checkpoint, take a log backup, observe log_reuse_wait_desc, and shrink the log if needed to reclaim space.

More information

The trace flag 9810 disables the In-Memory OLTP engine from reclaiming Thread Local Storage (TLS) memory, reverting to the behavior of SQL Server 2019.