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BACKUPBUFFER

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Description:

This wait type is when a backup thread is waiting for a buffer in which it will write backup data to then be written to a backup file. The description below is very old, as these waits occur for all backups.

(Books Online description: “Occurs when a backup task is waiting for data, or is waiting for a buffer in which to store data. This type is not typical, except when a task is waiting for a tape mount.”)

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Added in SQL Server version:

Pre-2005/2005

Removed in SQL Server version:

N/A

Extended Events wait_type value:

The map_key value in sys.dm_xe_map_values is 134 in 2008 and 2008 R2, and 138 in 2012 and 2014 RTM. After 2014 RTM, you must check the DMV to get the latest value as some map_key values have changed in later builds.

Other information:

These waits occur for all backups, with the cumulative wait time for all BACKUPBUFFER waits from a single backup approximately equaling the elapsed time of the backup. If the wait type becomes prevalent, see the BACKUPIO wait for more information.

Known occurrences in SQL Server (list number matches call stack list):

  1. Waiting for a buffer to write backup data into
  2. Waiting for a buffer to write backup data into

And other similar call stacks.

Abbreviated call stacks (list number matches known occurrences list):

  1. SOS_Task::PostWait+90
    EventInternal<SuspendQueueSLock>::Wait+1f9
    BackupSynchronizedBufferList::WaitForValidBuffer+c0
    BackupMedium::WriteDataStream+635
    BackupStream::DoFileBackup+1cb
    BackupStream::ThreadMainRoutine+123
    BackupThread::ThreadBase+51
    SubprocEntrypoint+a59
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+a8
  2. SOS_Task::PostWait+90
    EventInternal<SuspendQueueSLock>::Wait+1f9
    BackupSynchronizedBufferList::RemoveFreeBuffer+b8
    BackupOperation::CopyFileToBackupSet0+8d6
    BackupOperation::CopyFileToBackupSet+7d
    AsynchronousDiskAction::ExecuteDeferredAction+bf
    AsynchronousDiskWorker::ThreadRoutine+15c
    SubprocEntrypoint+a59
    SOS_Task::Param::Execute+21e
    SOS_Scheduler::RunTask+a8