HADR_XRF_STACK_ACCESS SQL Server Wait Type

Wait Type HADR_XRF_STACK_ACCESS

The wait type HADR_XRF_STACK_ACCESS is ranked #241 by Stedman Solutions and Database Health Monitor.

Wait statistics, in the context of SQL Server, refer to the amount of time that a query spends waiting to access data in the database. When a client application requests data from the database, the request is placed in a queue and the client application must wait for its turn to access the data. The time that the query spends waiting is called a "wait" and is tracked by SQL Server. This information can be used to identify potential performance bottlenecks and optimize the performance of the database. Wait statistics are commonly used by database administrators to diagnose and troubleshoot performance issues in SQL Server.


SQL Server Always On Availability Groups ensure high availability by coordinating synchronization between primary and secondary replicas. During these operations, specific wait types like HADR_XRF_STACK_ACCESS can occur. Understanding this wait type helps you optimize your Always On environment and address potential performance bottlenecks.

What is HADR_XRF_STACK_ACCESS?

The HADR_XRF_STACK_ACCESS wait type occurs when SQL Server is waiting to access the cross-replica stack used to coordinate tasks in an Always On Availability Group. This stack facilitates communication and synchronization between replicas, ensuring consistent operations and data replication. This wait type indicates that SQL Server is pausing while accessing or updating this shared resource.

In simpler terms, this wait means SQL Server is waiting for access to the internal mechanism that manages synchronization between the primary and secondary replicas.

Why Does HADR_XRF_STACK_ACCESS Happen?

Several factors can lead to HADR_XRF_STACK_ACCESS waits, including:

  • High transaction log activity on the primary replica creating a backlog of synchronization tasks.
  • Network latency or bandwidth limitations slowing down communication between replicas.
  • Resource bottlenecks, such as limited CPU or memory on replicas, delaying stack access.
  • Contention caused by multiple operations competing for access to the same resources.
  • Misconfigured Always On Availability Group settings or synchronization modes.

Identifying these factors is key to minimizing delays and ensuring smooth synchronization.

How to Monitor HADR_XRF_STACK_ACCESS Waits

Monitoring HADR_XRF_STACK_ACCESS waits is essential for diagnosing and resolving synchronization issues. The Database Health Monitor is a powerful tool for this purpose. Its Historic Waits Monitoring feature provides detailed insights into when these waits occur, how frequently they happen, and their impact on system performance.

By using Database Health Monitor, you can identify patterns in these waits and determine whether they are caused by network issues, resource limitations, or workload imbalances, allowing you to take targeted action.

What Can You Do About HADR_XRF_STACK_ACCESS Waits?

If you notice frequent or prolonged HADR_XRF_STACK_ACCESS waits, consider the following actions:

  • Ensure your network infrastructure has sufficient bandwidth and low latency to support Always On communication.
  • Allocate adequate resources (CPU, memory, and disk I/O) to both primary and secondary replicas.
  • Optimize workloads on the primary replica to reduce transaction log activity and synchronization overhead.
  • Review Always On Availability Group configurations and adjust synchronization modes to align with workload needs.
  • Distribute workloads across replicas to reduce contention for shared resources like the cross-replica stack.

These steps can help reduce synchronization delays and ensure the efficient operation of your Always On Availability Group.

Why Use Database Health Monitor?

The Database Health Monitor is an invaluable tool for tracking SQL Server wait types, including HADR_XRF_STACK_ACCESS. Its Historic Waits Monitoring feature provides actionable insights into wait trends, helping you identify and address bottlenecks in your Always On synchronization processes. With Database Health Monitor, you can ensure your SQL Server environment operates at peak performance.

Start using Database Health Monitor today to monitor and optimize your SQL Server’s performance, ensuring reliable and efficient Always On Availability Groups!


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Applies to

    Related Waits

    HADR_AG_MUTEX
    HADR_AR_CRITICAL_SECTION_ENTRY
    HADR_AR_MANAGER_MUTEX
    HADR_AR_UNLOAD_COMPLETED
    HADR_ARCONTROLLER_NOTIFICATIONS_SUBSCRIBER_LIST
    HADR_BACKUP_BULK_LOCK
    HADR_BACKUP_QUEUE
    HADR_CLUSAPI_CALL
    HADR_COMPRESSED_CACHE_SYNC
    HADR_CONNECTIVITY_INFO
    HADR_DATABASE_FLOW_CONTROL
    HADR_DATABASE_VERSIONING_STATE
    HADR_DATABASE_WAIT_FOR_RESTART
    HADR_DATABASE_WAIT_FOR_TRANSITION_TO_VERSIONING
    HADR_DB_COMMAND
    HADR_DB_OP_COMPLETION_SYNC
    HADR_DB_OP_START_SYNC
    HADR_DBR_SUBSCRIBER
    HADR_DBR_SUBSCRIBER_FILTER_LIST
    HADR_DBSEEDING
    HADR_DBSEEDING_LIST
    HADR_DBSTATECHANGE_SYNC
    HADR_FABRIC_CALLBACK
    HADR_FILESTREAM_BLOCK_FLUSH
    HADR_FILESTREAM_FILE_CLOSE
    HADR_FILESTREAM_FILE_REQUEST
    HADR_FILESTREAM_IOMGR
    HADR_FILESTREAM_MANAGER
    HADR_GROUP_COMMIT
    HADR_LOGCAPTURE_SYNC
    HADR_LOGCAPTURE_WAIT
    HADR_LOGPROGRESS_SYNC
    HADR_NOTIFICATION_DEQUEUE
    HADR_NOTIFICATION_WORKER_EXCLUSIVE_ACCESS
    HADR_NOTIFICATION_WORKER_STARTUP_SYNC
    HADR_NOTIFICATION_WORKER_TERMINATION_SYNC
    HADR_PARTNER_SYNC
    HADR_READ_ALL_NETWORKS
    HADR_RECOVERY_WAIT_FOR_CONNECTION
    HADR_RECOVERY_WAIT_FOR_UNDO
    HADR_REPLICAINFO_SYNC
    HADR_SYNC_COMMIT
    HADR_SYNCHRONIZING_THROTTLE
    HADR_TDS_LISTENER_SYNC
    HADR_TDS_LISTENER_SYNC_PROCESSING
    HADR_TIMER_TASK
    HADR_TRANSPORT_DBRLIST
    HADR_TRANSPORT_FLOW_CONTROL
    HADR_TRANSPORT_SESSION
    HADR_WORK_POOL
    HADR_WORK_QUEUE

    See Also


    All Wait Types
    HADR_XRF_STACK_ACCESS SQL Server Wait Type