WaitTypes

ASSEMBLY_LOAD Occurs during exclusive access to assembly loading.
ASYNC_DISKPOOL_LOCK Occurs when there is an attempt to synchronize parallel threads that are performing tasks such as creating or initializing a file.
ASYNC_IO_COMPLETION Occurs when a task is waiting for I/Os to finish.
ASYNC_NETWORK_IO
AUDIT_GROUPCACHE_LOCK Occurs when there is a wait on a lock that controls access to a special cache. The cache contains information about which audits are being used to audit each audit action group.
AUDIT_LOGINCACHE_LOCK Occurs when there is a wait on a lock that controls access to a special cache. The cache contains information about which audits are being used to audit login audit action groups.
AUDIT_ON_DEMAND_TARGET_LOCK Occurs when there is a wait on a lock that is used to ensure single initialization of audit related Extended Event targets.
AUDIT_XE_SESSION_MGR Occurs when there is a wait on a lock that is used to synchronize the starting and stopping of audit related Extended Events sessions.
BACKUP Occurs when a task is blocked as part of backup processing.
BACKUP_OPERATOR Occurs when a task is waiting for a tape mount. To view the tape status, query sys.dm_io_backup_tapes. If a mount operation is not pending, this wait type may indicate a hardware problem with the tape drive.
BACKUPBUFFER 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.
BACKUPIO 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.
BACKUPTHREAD Occurs when a task is waiting for a backup task to finish. Wait times may be long, from several minutes to several hours. If the task that is being waited on is in an I/O process, this type does not indicate a problem.
BAD_PAGE_PROCESS Occurs when the background suspect page logger is trying to avoid running more than every five seconds. Excessive suspect pages cause the logger to run frequently.
BMPALLOCATION Occurs with parallel batch-mode plans when synchronizing the allocation of a large bitmap filter. If waiting is excessive and cannot be reduced by tuning the query (such as adding indexes), consider adjusting the cost threshold for parallelism or lowering the degree of parallelism.
BMPBUILD Occurs with parallel batch-mode plans when synchronizing the building of a large bitmap filter. If waiting is excessive and cannot be reduced by tuning the query (such as adding indexes), consider adjusting the cost threshold for parallelism or lowering the degree of parallelism.
BMPREPARTITION Occurs with parallel batch-mode plans when synchronizing the repartitioning of a large bitmap filter. If waiting is excessive and cannot be reduced by tuning the query (such as adding indexes), consider adjusting the cost threshold for parallelism or lowering the degree of parallelism.
BMPREPLICATION Occurs with parallel batch-mode plans when synchronizing the replication of a large bitmap filter across worker threads. If waiting is excessive and cannot be reduced by tuning the query (such as adding indexes), consider adjusting the cost threshold for parallelism or lowering the degree of parallelism.
BPSORT Occurs with parallel batch-mode plans when synchronizing the sorting of a dataset across multiple threads. If waiting is excessive and cannot be reduced by tuning the query (such as adding indexes), consider adjusting the cost threshold for parallelism or lowering the degree of parallelism.
BROKER_CONNECTION_RECEIVE_TASK Occurs when waiting for access to receive a message on a connection endpoint. Receive access to the endpoint is serialized.
BROKER_ENDPOINT_STATE_MUTEX Occurs when there is contention to access the state of a Service Broker connection endpoint. Access to the state for changes is serialized.
BROKER_EVENTHANDLER Occurs when a task is waiting in the primary event handler of the Service Broker. This should occur very briefly.
BROKER_INIT Occurs when initializing Service Broker in each active database. This should occur infrequently.
BROKER_MASTERSTART Occurs when a task is waiting for the primary event handler of the Service Broker to start. This should occur very briefly.
BROKER_RECEIVE_WAITFOR Occurs when the RECEIVE WAITFOR is waiting. This may mean that either no messages are ready to be received in the queue or a lock contention is preventing it from receiving messages from the queue.
BROKER_REGISTERALLENDPOINTS Occurs during the initialization of a Service Broker connection endpoint. This should occur very briefly.
BROKER_SERVICE Occurs when the Service Broker destination list that is associated with a target service is updated or re-prioritized.
BROKER_SHUTDOWN Occurs when there is a planned shutdown of Service Broker. This should occur very briefly, if at all.
BROKER_TASK_STOP Occurs when the Service Broker queue task handler tries to shut down the task. The state check is serialized and must be in a running state beforehand.
BROKER_TO_FLUSH Occurs when the Service Broker lazy flusher flushes the in-memory transmission objects to a work table.
BROKER_TRANSMITTER Occurs when the Service Broker transmitter is waiting for work. Service Broker has a component known as the Transmitter which schedules messages from multiple dialogs to be sent across the wire over one or more connection endpoints. The transmitter has 2 dedicated threads for this purpose. This wait type is charged when these transmitter threads are waiting for dialog messages to be sent using the transport connections. High values of waiting_tasks_count for this wait type point to intermittent work for these transmitter threads and are not indications of any performance problem. If service broker is not used at all, waiting_tasks_count should be 2 (for the 2 transmitter threads) and wait_time_ms should be twice the duration since instance startup. See Service broker wait stats.
BUILTIN_HASHKEY_MUTEX May occur after startup of instance, while internal data structures are initializing. Will not recur once data structures have initialized.
CHECKPOINT_QUEUE Occurs while the checkpoint task is waiting for the next checkpoint request.
CHKPT Occurs at server startup to tell the checkpoint thread that it can start.
CLEAR_DB Occurs during operations that change the state of a database, such as opening or closing a database.
CLR_AUTO_EVENT Occurs when a task is currently performing common language runtime (CLR) execution and is waiting for a particular autoevent to be initiated. Long waits are typical, and do not indicate a problem.
CLR_CRST Occurs when a task is currently performing CLR execution and is waiting to enter a critical section of the task that is currently being used by another task.
CLR_JOIN Occurs when a task is currently performing CLR execution and waiting for another task to end. This wait state occurs when there is a join between tasks.
CLR_MANUAL_EVENT Occurs when a task is currently performing CLR execution and is waiting for a specific manual event to be initiated.
CLR_MEMORY_SPY Occurs during a wait on lock acquisition for a data structure that is used to record all virtual memory allocations that come from CLR. The data structure is locked to maintain its integrity if there is parallel access.
CLR_MONITOR Occurs when a task is currently performing CLR execution and is waiting to obtain a lock on the monitor.
CLR_RWLOCK_READER Occurs when a task is currently performing CLR execution and is waiting for a reader lock.
CLR_RWLOCK_WRITER Occurs when a task is currently performing CLR execution and is waiting for a writer lock.
CLR_SEMAPHORE Occurs when a task is currently performing CLR execution and is waiting for a semaphore.
CLR_TASK_START Occurs while waiting for a CLR task to complete startup.
CLRHOST_STATE_ACCESS Occurs where there is a wait to acquire exclusive access to the CLR-hosting data structures. This wait type occurs while setting up or tearing down the CLR runtime.
CMEMTHREAD Occurs when a task is waiting on a thread-safe memory object. The wait time might increase when there is contention caused by multiple tasks trying to allocate memory from the same memory object.
CXCONSUMER Occurs with parallel query plans when a consumer thread waits for a producer thread to send rows. This is a normal part of parallel query execution.
CXPACKET
CXROWSET_SYNC Occurs during a parallel range scan.
DAC_INIT Occurs while the dedicated administrator connection is initializing.
DBMIRROR_EVENTS_QUEUE Occurs when database mirroring waits for events to process.
DBMIRROR_SEND Occurs when a task is waiting for a communications backlog at the network layer to clear to be able to send messages. Indicates that the communications layer is starting to become overloaded and affect the database mirroring data throughput.
DBMIRROR_WORKER_QUEUE Indicates that the database mirroring worker task is waiting for more work.
DBMIRRORING_CMD Occurs when a task is waiting for log records to be flushed to disk. This wait state is expected to be held for long periods of time.
DEADLOCK_ENUM_MUTEX Occurs when the deadlock monitor and sys.dm_os_waiting_tasks try to make sure that SQL Server is not running multiple deadlock searches at the same time.
DEADLOCK_TASK_SEARCH Large waiting time on this resource indicates that the server is executing queries on top of sys.dm_os_waiting_tasks, and these queries are blocking deadlock monitor from running deadlock search. This wait type is used by deadlock monitor only. Queries on top of sys.dm_os_waiting_tasks use DEADLOCK_ENUM_MUTEX.
DEBUG Occurs during Transact-SQL and CLR debugging for internal synchronization.
DISABLE_VERSIONING Occurs when SQL Server polls the version transaction manager to see whether the timestamp of the earliest active transaction is later than the timestamp of when the state started changing. If this is this case, all the snapshot transactions that were started before the ALTER DATABASE statement was run have finished. This wait state is used when SQL Server disables versioning by using the ALTER DATABASE statement.
DISKIO_SUSPEND Occurs when a task is waiting to access a file when an external backup is active. This is reported for each waiting user process. A count larger than five per user process may indicate that the external backup is taking too much time to finish.
DISPATCHER_QUEUE_SEMAPHORE Occurs when a thread from the dispatcher pool is waiting for more work to process. The wait time for this wait type is expected to increase when the dispatcher is idle.
DLL_LOADING_MUTEX Occurs once while waiting for the XML parser DLL to load.
DROPTEMP Occurs between attempts to drop a temporary object if the previous attempt failed. The wait duration grows exponentially with each failed drop attempt.
DTC Occurs when a task is waiting on an event that is used to manage state transition. This state controls when the recovery of Microsoft Distributed Transaction Coordinator (MS DTC) transactions occurs after SQL Server receives notification that the MS DTC service has become unavailable.
DTC_ABORT_REQUEST Occurs in a MS DTC worker session when the session is waiting to take ownership of a MS DTC transaction. After MS DTC owns the transaction, the session can roll back the transaction. Generally, the session will wait for another session that is using the transaction.
DTC_RESOLVE Occurs when a recovery task is waiting for the master database in a cross-database transaction so that the task can query the outcome of the transaction.
DTC_STATE Occurs when a task is waiting on an event that protects changes to the internal MS DTC global state object. This state should be held for very short periods of time.
DTC_TMDOWN_REQUEST Occurs in a MS DTC worker session when SQL Server receives notification that the MS DTC service is not available. First, the worker will wait for the MS DTC recovery process to start. Then, the worker waits to obtain the outcome of the distributed transaction that the worker is working on. This may continue until the connection with the MS DTC service has been reestablished.
DTC_WAITFOR_OUTCOME Occurs when recovery tasks wait for MS DTC to become active to enable the resolution of prepared transactions.
DUMP_LOG_COORDINATOR Occurs when a main task is waiting for a subtask to generate data. Ordinarily, this state does not occur. A long wait indicates an unexpected blockage. The subtask should be investigated.
EE_PMOLOCK Occurs during synchronization of certain types of memory allocations during statement execution.
EE_SPECPROC_MAP_INIT Occurs during synchronization of internal procedure hash table creation. This wait can only occur during the initial accessing of the hash table after the SQL Server instance starts.
ENABLE_VERSIONING Occurs when SQL Server waits for all update transactions in this database to finish before declaring the database ready to transition to snapshot isolation allowed state. This state is used when SQL Server enables snapshot isolation by using the ALTER DATABASE statement.
ERROR_REPORTING_MANAGER Occurs during synchronization of multiple concurrent error log initializations.
EXCHANGE Occurs during synchronization in the query processor exchange iterator during parallel queries.
EXECSYNC Occurs during parallel queries while synchronizing in query processor in areas not related to the exchange iterator. Examples of such areas are bitmaps, large binary objects (LOBs), and the spool iterator. LOBs may frequently use this wait state.
EXECUTION_PIPE_EVENT_INTERNAL Occurs during synchronization between producer and consumer parts of batch execution that are submitted through the connection context.
FCB_REPLICA_READ Occurs when the reads of a snapshot (or a temporary snapshot created by DBCC) sparse file are synchronized.
FCB_REPLICA_WRITE Occurs when the pushing or pulling of a page to a snapshot (or a temporary snapshot created by DBCC) sparse file is synchronized.
FS_FC_RWLOCK Occurs when there is a wait by the FILESTREAM garbage collector to do either of the following:
FS_GARBAGE_COLLECTOR_SHUTDOWN Occurs when the FILESTREAM garbage collector is waiting for cleanup tasks to be completed.
FS_HEADER_RWLOCK Occurs when there is a wait to acquire access to the FILESTREAM header of a FILESTREAM data container to either read or update contents in the FILESTREAM header file (Filestream.hdr).
FS_LOGTRUNC_RWLOCK Occurs when there is a wait to acquire access to FILESTREAM log truncation to do either of the following:
FSA_FORCE_OWN_XACT Occurs when a FILESTREAM file I/O operation needs to bind to the associated transaction, but the transaction is currently owned by another session.
FSAGENT Occurs when a FILESTREAM file I/O operation is waiting for a FILESTREAM agent resource that is being used by another file I/O operation.
FSTR_CONFIG_MUTEX Occurs when there is a wait for another FILESTREAM feature reconfiguration to be completed.
FSTR_CONFIG_RWLOCK Occurs when there is a wait to serialize access to the FILESTREAM configuration parameters.
FT_COMPROWSET_RWLOCK Full-text is waiting on fragment metadata operation. Documented for informational purposes only. Not supported. Future compatibility is not guaranteed.
FT_IFTS_RWLOCK Full-text is waiting on internal synchronization. Documented for informational purposes only. Not supported. Future compatibility is not guaranteed.
FT_IFTS_SCHEDULER_IDLE_WAIT Full-text scheduler sleep wait type. The scheduler is idle.
FT_IFTSHC_MUTEX Full-text is waiting on an fdhost control operation. Documented for informational purposes only. Not supported. Future compatibility is not guaranteed.
FT_IFTSISM_MUTEX Full-text is waiting on communication operation. Documented for informational purposes only. Not supported. Future compatibility is not guaranteed.
FT_MASTER_MERGE Full-text is waiting on master merge operation. Documented for informational purposes only. Not supported. Future compatibility is not guaranteed.
FT_RESTART_CRAWL Occurs when a full-text crawl needs to restart from a last known good point to recover from a transient failure. The wait lets the worker tasks currently working on that population to complete or exit the current step.
FULLTEXT GATHERER Occurs during synchronization of full-text operations.
HADR_AG_MUTEX Occurs when an Always On DDL statement or Windows Server Failover Clustering command is waiting for exclusive read/write access to the configuration of an availability group.,
HADR_AR_CRITICAL_SECTION_ENTRY Occurs when an Always On DDL statement or Windows Server Failover Clustering command is waiting for exclusive read/write access to the runtime state of the local replica of the associated availability group.,
HADR_AR_MANAGER_MUTEX Occurs when an availability replica shutdown is waiting for startup to complete or an availability replica startup is waiting for shutdown to complete. Internal use only.,
HADR_ARCONTROLLER_NOTIFICATIONS_SUBSCRIBER_LIST The publisher for an availability replica event (such as a state change or configuration change) is waiting for exclusive read/write access to the list of event subscribers. Internal use only.,
HADR_BACKUP_BULK_LOCK The Always On primary database received a backup request from a secondary database and is waiting for the background thread to finish processing the request on acquiring or releasing the BulkOp lock.,
HADR_BACKUP_QUEUE The backup background thread of the Always On primary database is waiting for a new work request from the secondary database. (typically, this occurs when the primary database is holding the BulkOp log and is waiting for the secondary database to indicate that the primary database can release the lock).,
HADR_CLUSAPI_CALL A SQL Server thread is waiting to switch from non-preemptive mode (scheduled by SQL Server) to preemptive mode (scheduled by the operating system) in order to invoke Windows Server Failover Clustering APIs.,
HADR_COMPRESSED_CACHE_SYNC Waiting for access to the cache of compressed log blocks that is used to avoid redundant compression of the log blocks sent to multiple secondary databases.,
HADR_DATABASE_FLOW_CONTROL Waiting for messages to be sent to the partner when the maximum number of queued messages has been reached. Indicates that the log scans are running faster than the network sends. This is an issue only if network sends are slower than expected.,
HADR_DATABASE_VERSIONING_STATE Occurs on the versioning state change of an Always On secondary database. This wait is for internal data structures and is usually is very short with no direct effect on data access.,
HADR_DATABASE_WAIT_FOR_RESTART Waiting for the database to restart under Always On Availability Groups control. Under normal conditions, this is not a customer issue because waits are expected here.,
HADR_DATABASE_WAIT_FOR_TRANSITION_TO_VERSIONING A query on object(s) in a readable secondary database of an Always On availability group is blocked on row versioning while waiting for commit or rollback of all transactions that were in-flight when the secondary replica was enabled for read workloads. This wait type guarantees that row versions are available before execution of a query under snapshot isolation.,
HADR_DB_COMMAND Waiting for responses to conversational messages (which require an explicit response from the other side, using the Always On conversational message infrastructure). A number of different message types use this wait type.,
HADR_DB_OP_COMPLETION_SYNC Waiting for responses to conversational messages (which require an explicit response from the other side, using the Always On conversational message infrastructure). A number of different message types use this wait type.,
HADR_DB_OP_START_SYNC An Always On DDL statement or a Windows Server Failover Clustering command is waiting for serialized access to an availability database and its runtime state.,
HADR_DBR_SUBSCRIBER The publisher for an availability replica event (such as a state change or configuration change) is waiting for exclusive read/write access to the runtime state of an event subscriber that corresponds to an availability database. Internal use only.,
HADR_DBR_SUBSCRIBER_FILTER_LIST The publisher for an availability replica event (such as a state change or configuration change) is waiting for exclusive read/write access to the list of event subscribers that correspond to availability databases. Internal use only.,
HADR_DBSTATECHANGE_SYNC Concurrency control wait for updating the internal state of the database replica.,
HADR_FILESTREAM_BLOCK_FLUSH The FILESTREAM Always On transport manager is waiting until processing of a log block is finished.,
HADR_FILESTREAM_FILE_CLOSE The FILESTREAM Always On transport manager is waiting until the next FILESTREAM file gets processed and its handle gets closed.,
HADR_FILESTREAM_FILE_REQUEST An Always On secondary replica is waiting for the primary replica to send all requested FILESTREAM files during UNDO.,
HADR_FILESTREAM_IOMGR The FILESTREAM Always On transport manager is waiting for R/W lock that protects the FILESTREAM Always On I/O manager during startup or shutdown.,
HADR_FILESTREAM_IOMGR_IOCOMPLETION The FILESTREAM Always On I/O manager is waiting for I/O completion.,
HADR_FILESTREAM_MANAGER The FILESTREAM Always On transport manager is waiting for the R/W lock that protects the FILESTREAM Always On transport manager during startup or shutdown.,
HADR_GROUP_COMMIT Transaction commit processing is waiting to allow a group commit so that multiple commit log records can be put into a single log block. This wait is an expected condition that optimizes the log I/O, capture, and send operations.,
HADR_LOGCAPTURE_SYNC Concurrency control around the log capture or apply object when creating or destroying scans. This is an expected wait when partners change state or connection status.,
HADR_LOGCAPTURE_WAIT Waiting for log records to become available. Can occur either when waiting for new log records to be generated by connections or for I/O completion when reading log not in the cache. This is an expected wait if the log scan is caught up to the end of log or is reading from disk.,
HADR_LOGPROGRESS_SYNC Concurrency control wait when updating the log progress status of database replicas.,
HADR_NOTIFICATION_DEQUEUE A background task that processes Windows Server Failover Clustering notifications is waiting for the next notification. Internal use only.,
HADR_NOTIFICATION_WORKER_EXCLUSIVE_ACCESS The Always On availability replica manager is waiting for serialized access to the runtime state of a background task that processes Windows Server Failover Clustering notifications. Internal use only.,
HADR_NOTIFICATION_WORKER_STARTUP_SYNC A background task is waiting for the completion of the startup of a background task that processes Windows Server Failover Clustering notifications. Internal use only.,
HADR_NOTIFICATION_WORKER_TERMINATION_SYNC A background task is waiting for the termination of a background task that processes Windows Server Failover Clustering notifications. Internal use only.,
HADR_PARTNER_SYNC Concurrency control wait on the partner list.,
HADR_READ_ALL_NETWORKS Waiting to get read or write access to the list of WSFC networks. Internal use only. Note: The engine keeps a list of WSFC networks that is used in dynamic management views (such as sys.dm_hadr_cluster_networks) or to validate Always On Transact-SQL statements that reference WSFC network information. This list is updated upon engine startup, WSFC related notifications, and internal Always On restart (for example, losing and regaining of WSFC quorum). Tasks will usually be blocked when an update in that list is in progress. ,
HADR_RECOVERY_WAIT_FOR_CONNECTION Waiting for the secondary database to connect to the primary database before running recovery. This is an expected wait, which can lengthen if the connection to the primary is slow to establish.,
HADR_RECOVERY_WAIT_FOR_UNDO Database recovery is waiting for the secondary database to finish the reverting and initializing phase to bring it back to the common log point with the primary database. This is an expected wait after failovers.Undo progress can be tracked through the Windows System Monitor (perfmon.exe) and dynamic management views.,
HADR_REPLICAINFO_SYNC Waiting for concurrency control to update the current replica state.,
HADR_SYNC_COMMIT Waiting for transaction commit processing for the synchronized secondary databases to harden the log. This wait is also reflected by the Transaction Delay performance counter. This wait type is expected for synchronized availability groups and indicates the time to send, write, and acknowledge log to the secondary databases.,
HADR_SYNCHRONIZING_THROTTLE Waiting for transaction commit processing to allow a synchronizing secondary database to catch up to the primary end of log in order to transition to the synchronized state. This is an expected wait when a secondary database is catching up.,
HADR_TDS_LISTENER_SYNC Either the internal Always On system or the WSFC cluster will request that listeners are started or stopped. The processing of this request is always asynchronous, and there is a mechanism to remove redundant requests. There are also moments that this process is suspended because of configuration changes. All waits related with this listener synchronization mechanism use this wait type. Internal use only.,
HADR_TDS_LISTENER_SYNC_PROCESSING Used at the end of an Always On Transact-SQL statement that requires starting and/or stopping an availability group listener. Since the start/stop operation is done asynchronously, the user thread will block using this wait type until the situation of the listener is known.,
HADR_THROTTLE_LOG_RATE_MISMATCHED_SLO Occurs when a geo-replication secondary is configured with lower compute size (lower SLO) than the primary. A primary database is throttled due to delayed log consumption by the secondary. This is caused by the secondary database having insufficient compute capacity to keep up with the primary database's rate of change.
HADR_TIMER_TASK Waiting to get the lock on the timer task object and is also used for the actual waits between times that work is being performed. For example, for a task that runs every 10 seconds, after one execution, Always On Availability Groups waits about 10 seconds to reschedule the task, and the wait is included here.,
HADR_TRANSPORT_DBRLIST Waiting for access to the transport layer's database replica list. Used for the spinlock that grants access to it.,
HADR_TRANSPORT_FLOW_CONTROL Waiting when the number of outstanding unacknowledged Always On messages is over the out flow control threshold. This is on an availability replica-to-replica basis (not on a database-to-database basis).,
HADR_TRANSPORT_SESSION Always On Availability Groups is waiting while changing or accessing the underlying transport state.,
HADR_WORK_POOL Concurrency control wait on the Always On Availability Groups background work task object.,
HADR_WORK_QUEUE Always On Availability Groups background worker thread waiting for new work to be assigned. This is an expected wait when there are ready workers waiting for new work, which is the normal state.,
HADR_XRF_STACK_ACCESS Accessing (look up, add, and delete) the extended recovery fork stack for an Always On availability database.,
HTBUILD Occurs with parallel batch-mode plans when synchronizing the building of the hash table on the input side of a hash join/aggregation. If waiting is excessive and cannot be reduced by tuning the query (such as adding indexes), consider adjusting the cost threshold for parallelism or lowering the degree of parallelism.
HTDELETE Occurs with parallel batch-mode plans when synchronizing at the end of a hash join/aggregation. If waiting is excessive and cannot be reduced by tuning the query (such as adding indexes), consider adjusting the cost threshold for parallelism or lowering the degree of parallelism.
HTMEMO Occurs with parallel batch-mode plans when synchronizing before scanning hash table to output matches / non-matches in hash join/aggregation. If waiting is excessive and cannot be reduced by tuning the query (such as adding indexes), consider adjusting the cost threshold for parallelism or lowering the degree of parallelism.
HTREINIT Occurs with parallel batch-mode plans when synchronizing before resetting a hash join/aggregation for the next partial join. If waiting is excessive and cannot be reduced by tuning the query (such as adding indexes), consider adjusting the cost threshold for parallelism or lowering the degree of parallelism.
HTREPARTITION Occurs with parallel batch-mode plans when synchronizing the repartitioning of the hash table on the input side of a hash join/aggregation. If waiting is excessive and cannot be reduced by tuning the query (such as adding indexes), consider adjusting the cost threshold for parallelism or lowering the degree of parallelism.
HTTP_ENUMERATION Occurs at startup to enumerate the HTTP endpoints to start HTTP.
HTTP_START Occurs when a connection is waiting for HTTP to complete initialization.
IMPPROV_IOWAIT Occurs when SQL Server waits for a bulkload I/O to finish.
IO_AUDIT_MUTEX Occurs during synchronization of trace event buffers.
IO_COMPLETION Occurs while waiting for I/O operations to complete. This wait type generally represents non-data page I/Os. Data page I/O completion waits appear as PAGEIOLATCH_* waits.
IO_RETRY Occurs when an I/O operation such as a read or a write to disk fails because of insufficient resources, and is then retried.
KSOURCE_WAKEUP Used by the service control task while waiting for requests from the Service Control Manager. Long waits are expected and do not indicate a problem.
LATCH_DT Occurs when waiting for a DT (destroy) latch. This does not include buffer latches or transaction mark latches. A listing of LATCH_* waits is available in sys.dm_os_latch_stats. Note that sys.dm_os_latch_stats groups LATCH_NL, LATCH_SH, LATCH_UP, LATCH_EX, and LATCH_DT waits together.
LATCH_EX Occurs when waiting for an EX (exclusive) latch. This does not include buffer latches or transaction mark latches. A listing of LATCH_* waits is available in sys.dm_os_latch_stats. Note that sys.dm_os_latch_stats groups LATCH_NL, LATCH_SH, LATCH_UP, LATCH_EX, and LATCH_DT waits together.
LATCH_KP Occurs when waiting for a KP (keep) latch. This does not include buffer latches or transaction mark latches. A listing of LATCH_* waits is available in sys.dm_os_latch_stats. Note that sys.dm_os_latch_stats groups LATCH_NL, LATCH_SH, LATCH_UP, LATCH_EX, and LATCH_DT waits together.
LATCH_SH Occurs when waiting for an SH (share) latch. This does not include buffer latches or transaction mark latches. A listing of LATCH_* waits is available in sys.dm_os_latch_stats. Note that sys.dm_os_latch_stats groups LATCH_NL, LATCH_SH, LATCH_UP, LATCH_EX, and LATCH_DT waits together.
LATCH_UP Occurs when waiting for an UP (update) latch. This does not include buffer latches or transaction mark latches. A listing of LATCH_* waits is available in sys.dm_os_latch_stats. Note that sys.dm_os_latch_stats groups LATCH_NL, LATCH_SH, LATCH_UP, LATCH_EX, and LATCH_DT waits together.
LAZYWRITER_SLEEP Occurs when lazy writer tasks are suspended. This is a measure of the time spent by background tasks that are waiting. Do not consider this state when you are looking for user stalls.
LCK_M_BU Occurs when a task is waiting to acquire a Bulk Update (BU) lock.
LCK_M_BU_ABORT_BLOCKERS Occurs when a task is waiting to acquire a Bulk Update (BU) lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_BU_LOW_PRIORITY Occurs when a task is waiting to acquire a Bulk Update (BU) lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_IS Occurs when a task is waiting to acquire an Intent Shared (IS) lock.
LCK_M_IS_ABORT_BLOCKERS Occurs when a task is waiting to acquire an Intent Shared (IS) lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_IS_LOW_PRIORITY Occurs when a task is waiting to acquire an Intent Shared (IS) lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_IU Occurs when a task is waiting to acquire an Intent Update (IU) lock.
LCK_M_IU_ABORT_BLOCKERS Occurs when a task is waiting to acquire an Intent Update (IU) lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_IU_LOW_PRIORITY Occurs when a task is waiting to acquire an Intent Update (IU) lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_IX Occurs when a task is waiting to acquire an Intent Exclusive (IX) lock.
LCK_M_IX_ABORT_BLOCKERS Occurs when a task is waiting to acquire an Intent Exclusive (IX) lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_IX_LOW_PRIORITY Occurs when a task is waiting to acquire an Intent Exclusive (IX) lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RIn_NL Occurs when a task is waiting to acquire a NULL lock on the current key value, and an Insert Range lock between the current and previous key. A NULL lock on the key is an instant release lock.
LCK_M_RIn_NL_ABORT_BLOCKERS Occurs when a task is waiting to acquire a NULL lock with Abort Blockers on the current key value, and an Insert Range lock with Abort Blockers between the current and previous key. A NULL lock on the key is an instant release lock. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RIn_NL_LOW_PRIORITY Occurs when a task is waiting to acquire a NULL lock with Low Priority on the current key value, and an Insert Range lock with Low Priority between the current and previous key. A NULL lock on the key is an instant release lock. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RIn_S Occurs when a task is waiting to acquire a shared lock on the current key value, and an Insert Range lock between the current and previous key.
LCK_M_RIn_S_ABORT_BLOCKERS Occurs when a task is waiting to acquire a shared lock with Abort Blockers on the current key value, and an Insert Range lock with Abort Blockers between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RIn_S_LOW_PRIORITY Occurs when a task is waiting to acquire a shared lock with Low Priority on the current key value, and an Insert Range lock with Low Priority between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RIn_U Task is waiting to acquire an Update lock on the current key value, and an Insert Range lock between the current and previous key.
LCK_M_RIn_U_ABORT_BLOCKERS Task is waiting to acquire an Update lock with Abort Blockers on the current key value, and an Insert Range lock with Abort Blockers between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RIn_U_LOW_PRIORITY Task is waiting to acquire an Update lock with Low Priority on the current key value, and an Insert Range lock with Low Priority between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RIn_X Occurs when a task is waiting to acquire an Exclusive lock on the current key value, and an Insert Range lock between the current and previous key.
LCK_M_RIn_X_ABORT_BLOCKERS Occurs when a task is waiting to acquire an Exclusive lock with Abort Blockers on the current key value, and an Insert Range lock with Abort Blockers between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RIn_X_LOW_PRIORITY Occurs when a task is waiting to acquire an Exclusive lock with Low Priority on the current key value, and an Insert Range lock with Low Priority between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RS_S Occurs when a task is waiting to acquire a Shared lock on the current key value, and a Shared Range lock between the current and previous key.
LCK_M_RS_S_ABORT_BLOCKERS Occurs when a task is waiting to acquire a Shared lock with Abort Blockers on the current key value, and a Shared Range lock with Abort Blockers between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RS_S_LOW_PRIORITY Occurs when a task is waiting to acquire a Shared lock with Low Priority on the current key value, and a Shared Range lock with Low Priority between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RS_U Occurs when a task is waiting to acquire an Update lock on the current key value, and an Update Range lock between the current and previous key.
LCK_M_RS_U_ABORT_BLOCKERS Occurs when a task is waiting to acquire an Update lock with Abort Blockers on the current key value, and an Update Range lock with Abort Blockers between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RS_U_LOW_PRIORITY Occurs when a task is waiting to acquire an Update lock with Low Priority on the current key value, and an Update Range lock with Low Priority between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RX_S Occurs when a task is waiting to acquire a Shared lock on the current key value, and an Exclusive Range lock between the current and previous key.
LCK_M_RX_S_ABORT_BLOCKERS Occurs when a task is waiting to acquire a Shared lock with Abort Blockers on the current key value, and an Exclusive Range with Abort Blockers lock between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RX_S_LOW_PRIORITY Occurs when a task is waiting to acquire a Shared lock with Low Priority on the current key value, and an Exclusive Range with Low Priority lock between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RX_U Occurs when a task is waiting to acquire an Update lock on the current key value, and an Exclusive range lock between the current and previous key.
LCK_M_RX_U_ABORT_BLOCKERS Occurs when a task is waiting to acquire an Update lock with Abort Blockers on the current key value, and an Exclusive range lock with Abort Blockers between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RX_U_LOW_PRIORITY Occurs when a task is waiting to acquire an Update lock with Low Priority on the current key value, and an Exclusive range lock with Low Priority between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RX_X Occurs when a task is waiting to acquire an Exclusive lock on the current key value, and an Exclusive Range lock between the current and previous key.
LCK_M_RX_X_ABORT_BLOCKERS Occurs when a task is waiting to acquire an Exclusive lock with Abort Blockers on the current key value, and an Exclusive Range lock with Abort Blockers between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_RX_X_LOW_PRIORITY Occurs when a task is waiting to acquire an Exclusive lock with Low Priority on the current key value, and an Exclusive Range lock with Low Priority between the current and previous key. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_S Occurs when a task is waiting to acquire a Shared lock.
LCK_M_S_ABORT_BLOCKERS Occurs when a task is waiting to acquire a Shared lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_S_LOW_PRIORITY Occurs when a task is waiting to acquire a Shared lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_SCH_M Occurs when a task is waiting to acquire a Schema Modify lock.
LCK_M_SCH_M_ABORT_BLOCKERS Occurs when a task is waiting to acquire a Schema Modify lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_SCH_M_LOW_PRIORITY Occurs when a task is waiting to acquire a Schema Modify lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_SCH_S Occurs when a task is waiting to acquire a Schema Share lock.
LCK_M_SCH_S_ABORT_BLOCKERS Occurs when a task is waiting to acquire a Schema Share lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_SCH_S_LOW_PRIORITY Occurs when a task is waiting to acquire a Schema Share lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_SIU Occurs when a task is waiting to acquire a Shared With Intent Update lock.
LCK_M_SIU_ABORT_BLOCKERS Occurs when a task is waiting to acquire a Shared With Intent Update lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_SIU_LOW_PRIORITY Occurs when a task is waiting to acquire a Shared With Intent Update lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_SIX Occurs when a task is waiting to acquire a Shared With Intent Exclusive lock.
LCK_M_SIX_ABORT_BLOCKERS Occurs when a task is waiting to acquire a Shared With Intent Exclusive lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_SIX_LOW_PRIORITY Occurs when a task is waiting to acquire a Shared With Intent Exclusive lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_U Occurs when a task is waiting to acquire an Update lock.
LCK_M_U_ABORT_BLOCKERS Occurs when a task is waiting to acquire an Update lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_U_LOW_PRIORITY Occurs when a task is waiting to acquire an Update lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_UIX Occurs when a task is waiting to acquire an Update With Intent Exclusive lock.
LCK_M_UIX_ABORT_BLOCKERS Occurs when a task is waiting to acquire an Update With Intent Exclusive lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_UIX_LOW_PRIORITY Occurs when a task is waiting to acquire an Update With Intent Exclusive lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_X Occurs when a task is waiting to acquire an Exclusive lock.
LCK_M_X_ABORT_BLOCKERS Occurs when a task is waiting to acquire an Exclusive lock with Abort Blockers. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LCK_M_X_LOW_PRIORITY Occurs when a task is waiting to acquire an Exclusive lock with Low Priority. (Related to the low priority wait option of ALTER TABLE and ALTER INDEX.),
LOGBUFFER Occurs when a task is waiting for space in the log buffer to store a log record. Consistently high values may indicate that the log devices cannot keep up with the amount of log being generated by the server.
LOGMGR Occurs when a task is waiting for any outstanding log I/Os to finish before shutting down the log while closing the database.
LOGMGR_QUEUE Occurs while the log writer task waits for work requests.
LOGMGR_RESERVE_APPEND Occurs when a task is waiting to see whether log truncation frees up log space to enable the task to write a new log record. Consider increasing the size of the log file(s) for the affected database to reduce this wait.
LOWFAIL_MEMMGR_QUEUE Occurs while waiting for memory to be available for use.
MEMORY_ALLOCATION_EXT Occurs while allocating memory from either the internal SQL Server memory pool or the operation system.,
MSQL_DQ Occurs when a task is waiting for a distributed query operation to finish. This is used to detect potential Multiple Active Result Set (MARS) application deadlocks. The wait ends when the distributed query call finishes.
MSQL_XACT_MGR_MUTEX Occurs when a task is waiting to obtain ownership of the session transaction manager to perform a session level transaction operation.
MSQL_XACT_MUTEX Occurs during synchronization of transaction usage. A request must acquire the mutex before it can use the transaction.
MSQL_XP Occurs when a task is waiting for an extended stored procedure to end. SQL Server uses this wait state to detect potential MARS application deadlocks. The wait stops when the extended stored procedure call ends.
MSSEARCH Occurs during Full-Text Search calls. This wait ends when the full-text operation completes. It does not indicate contention, but rather the duration of full-text operations.
NET_WAITFOR_PACKET Occurs when a connection is waiting for a network packet during a network read.
NETWORKIO
OLEDB Occurs when SQL Server calls the SQL Server Native Client OLE DB Provider. This wait type is not used for synchronization. Instead, it indicates the duration of calls to the OLE DB provider.
ONDEMAND_TASK_QUEUE Occurs while a background task waits for high priority system task requests. Long wait times indicate that there have been no high priority requests to process, and should not cause concern.
PAGEIOLATCH_DT Occurs when a task is waiting on a latch for a buffer that is in an I/O request. The latch request is in Destroy mode. Long waits may indicate problems with the disk subsystem.
PAGEIOLATCH_EX
PAGEIOLATCH_KP Occurs when a task is waiting on a latch for a buffer that is in an I/O request. The latch request is in Keep mode. Long waits may indicate problems with the disk subsystem.
PAGEIOLATCH_SH Occurs when a task is waiting on a latch for a buffer that is in an I/O request. The latch request is in Shared mode. Long waits may indicate problems with the disk subsystem.
PAGEIOLATCH_UP Occurs when a task is waiting on a latch for a buffer that is in an I/O request. The latch request is in Update mode. Long waits may indicate problems with the disk subsystem.
PAGELATCH_DT Occurs when a task is waiting on a latch for a buffer that is not in an I/O request. The latch request is in Destroy mode.
PAGELATCH_EX Occurs when a task is waiting on a latch for a buffer that is not in an I/O request. The latch request is in Exclusive mode.
PAGELATCH_KP Occurs when a task is waiting on a latch for a buffer that is not in an I/O request. The latch request is in Keep mode.
PAGELATCH_SH Occurs when a task is waiting on a latch for a buffer that is not in an I/O request. The latch request is in Shared mode.
PAGELATCH_UP Occurs when a task is waiting on a latch for a buffer that is not in an I/O request. The latch request is in Update mode.
PARALLEL_BACKUP_QUEUE Occurs when serializing output produced by RESTORE HEADERONLY, RESTORE FILELISTONLY, or RESTORE LABELONLY.
PREEMPTIVE_AUDIT_ACCESS_EVENTLOG Occurs when the SQL Server Operating System (SQLOS) scheduler switches to preemptive mode to write an audit event to the Windows event log.
PREEMPTIVE_AUDIT_ACCESS_SECLOG Occurs when the SQLOS scheduler switches to preemptive mode to write an audit event to the Windows Security log.
PREEMPTIVE_CLOSEBACKUPMEDIA Occurs when the SQLOS scheduler switches to preemptive mode to close backup media.
PREEMPTIVE_CLOSEBACKUPTAPE Occurs when the SQLOS scheduler switches to preemptive mode to close a tape backup device.
PREEMPTIVE_CLOSEBACKUPVDIDEVICE Occurs when the SQLOS scheduler switches to preemptive mode to close a virtual backup device.
PREEMPTIVE_CLUSAPI_CLUSTERRESOURCECONTROL Occurs when the SQLOS scheduler switches to preemptive mode to perform Windows failover cluster operations.
PREEMPTIVE_COM_COCREATEINSTANCE Occurs when the SQLOS scheduler switches to preemptive mode to create a COM object.
PREEMPTIVE_HADR_LEASE_MECHANISM Always On Availability Groups lease manager scheduling for Microsoft Support diagnostics.,
PRINT_ROLLBACK_PROGRESS Used to wait while user processes are ended in a database that has been transitioned by using the ALTER DATABASE termination clause. For more information, see ALTER DATABASE (Transact-SQL).
PWAIT_HADR_CHANGE_NOTIFIER_TERMINATION_SYNC Occurs when a background task is waiting for the termination of the background task that receives (via polling) Windows Server Failover Clustering notifications.,
PWAIT_HADR_CLUSTER_INTEGRATION An append, replace, and/or remove operation is waiting to grab a write lock on an Always On internal list (such as a list of networks, network addresses, or availability group listeners). Internal use only,
PWAIT_HADR_OFFLINE_COMPLETED An Always On drop availability group operation is waiting for the target availability group to go offline before destroying Windows Server Failover Clustering objects.,
PWAIT_HADR_ONLINE_COMPLETED An Always On create or failover availability group operation is waiting for the target availability group to come online.,
PWAIT_HADR_POST_ONLINE_COMPLETED An Always On drop availability group operation is waiting for the termination of any background task that was scheduled as part of a previous command. For example, there may be a background task that is transitioning availability databases to the primary role. The DROP AVAILABILITY GROUP DDL must wait for this background task to terminate in order to avoid race conditions.,
PWAIT_MD_LOGIN_STATS Occurs during internal synchronization in metadata on login stats.,
PWAIT_MD_RELATION_CACHE Occurs during internal synchronization in metadata on table or index.,
PWAIT_MD_SERVER_CACHE Occurs during internal synchronization in metadata on linked servers.,
PWAIT_MD_UPGRADE_CONFIG Occurs during internal synchronization in upgrading server wide configurations.,
QPJOB_KILL Indicates that an asynchronous automatic statistics update was canceled by a call to KILL as the update was starting to run. The terminating thread is suspended, waiting for it to start listening for KILL commands. A good value is less than one second.
QPJOB_WAITFOR_ABORT Indicates that an asynchronous automatic statistics update was canceled by a call to KILL when it was running. The update has now completed but is suspended until the terminating thread message coordination is complete. This is an ordinary but rare state, and should be very short. A good value is less than one second.
QRY_MEM_GRANT_INFO_MUTEX Occurs when Query Execution memory management tries to control access to static grant information list. This state lists information about the current granted and waiting memory requests. This state is a simple access control state. There should never be a long wait on this state. If this mutex is not released, all new memory-using queries will stop responding.
QUERY_ERRHDL_SERVICE_DONE Identified for informational purposes only. Not supported.
QUERY_EXECUTION_INDEX_SORT_EVENT_OPEN Occurs in certain cases when offline create index build is run in parallel, and the different worker threads that are sorting synchronize access to the sort files.
QUERY_NOTIFICATION_MGR_MUTEX Occurs during synchronization of the garbage collection queue in the Query Notification Manager.
QUERY_NOTIFICATION_SUBSCRIPTION_MUTEX Occurs during state synchronization for transactions in Query Notifications.
QUERY_NOTIFICATION_TABLE_MGR_MUTEX Occurs during internal synchronization within the Query Notification Manager.
QUERY_OPTIMIZER_PRINT_MUTEX Occurs during synchronization of query optimizer diagnostic output production. This wait type only occurs if diagnostic settings have been enabled under direction of Microsoft Product Support.
QUERY_WAIT_ERRHDL_SERVICE Identified for informational purposes only. Not supported.
RBIO_RG_DESTAGE Occurs when a Hyperscale database compute node is being throttled due to delayed log consumption by the long term log storage.
RBIO_RG_LOCALDESTAGE Occurs when a Hyperscale database compute node is being throttled due to delayed log consumption by the log service.
RBIO_RG_REPLICA Occurs when a Hyperscale database compute node is being throttled due to delayed log consumption by the readable secondary replica node(s).
RBIO_RG_STORAGE Occurs when a Hyperscale database compute node is being throttled due to delayed log consumption at the page server(s).
RECOVER_CHANGEDB Occurs during synchronization of database status in warm standby database.
REPL_CACHE_ACCESS Occurs during synchronization on a replication article cache. During these waits, the replication log reader stalls, and data definition language (DDL) statements on a published table are blocked.
REPL_SCHEMA_ACCESS Occurs during synchronization of replication schema version information. This state exists when DDL statements are executed on the replicated object, and when the log reader builds or consumes versioned schema based on DDL occurrence. Contention can be seen on this wait type if you have many published databases on a single publisher with transactional replication and the published databases are very active.
REPLICA_WRITES Occurs while a task waits for completion of page writes to database snapshots or DBCC replicas.
REQUEST_DISPENSER_PAUSE Occurs when a task is waiting for all outstanding I/O to complete, so that I/O to a file can be frozen for snapshot backup.
REQUEST_FOR_DEADLOCK_SEARCH Occurs while the deadlock monitor waits to start the next deadlock search. This wait is expected between deadlock detections, and lengthy total waiting time on this resource does not indicate a problem.
RESMGR_THROTTLED Occurs when a new request comes in and is throttled based on the GROUP_MAX_REQUESTS setting.
RESOURCE_QUEUE Occurs during synchronization of various internal resource queues.
RESOURCE_SEMAPHORE Occurs when a query memory request cannot be granted immediately due to other concurrent queries. High waits and wait times may indicate excessive number of concurrent queries, or excessive memory request amounts.
RESOURCE_SEMAPHORE_MUTEX Occurs while a query waits for its request for a thread reservation to be fulfilled. It also occurs when synchronizing query compile and memory grant requests.
RESOURCE_SEMAPHORE_QUERY_COMPILE Occurs when the number of concurrent query compilations reaches a throttling limit. High waits and wait times may indicate excessive compilations, recompiles, or uncachable plans.
RESOURCE_SEMAPHORE_SMALL_QUERY Occurs when memory request by a small query cannot be granted immediately due to other concurrent queries. Wait time should not exceed more than a few seconds, because the server transfers the request to the main query memory pool if it fails to grant the requested memory within a few seconds. High waits may indicate an excessive number of concurrent small queries while the main memory pool is blocked by waiting queries.
SEC_DROP_TEMP_KEY Occurs after a failed attempt to drop a temporary security key before a retry attempt.
SECURITY_MUTEX Occurs when there is a wait for mutexes that control access to the global list of Extensible Key Management (EKM) cryptographic providers and the session-scoped list of EKM sessions.
SEQUENTIAL_GUID Occurs while a new sequential GUID is being obtained.
SERVER_IDLE_CHECK Occurs during synchronization of SQL Server instance idle status when a resource monitor is attempting to declare a SQL Server instance as idle or trying to wake up.
SHUTDOWN Occurs while a shutdown statement waits for active connections to exit.
SLEEP_BPOOL_FLUSH Occurs when a checkpoint is throttling the issuance of new I/Os in order to avoid flooding the disk subsystem.
SLEEP_DBSTARTUP Occurs during database startup while waiting for all databases to recover.
SLEEP_DCOMSTARTUP Occurs once at most during SQL Server instance startup while waiting for DCOM initialization to complete.
SLEEP_MSDBSTARTUP Occurs when SQL Trace waits for the msdb database to complete startup.
SLEEP_SYSTEMTASK Occurs during the start of a background task while waiting for tempdb to complete startup.
SLEEP_TASK Occurs when a task sleeps while waiting for a generic event to occur.
SLEEP_TEMPDBSTARTUP Occurs while a task waits for tempdb to complete startup.
SNI_CRITICAL_SECTION Occurs during internal synchronization within SQL Server networking components.
SNI_HTTP_WAITFOR_0_DISCON Occurs during SQL Server shutdown, while waiting for outstanding HTTP connections to exit.
SNI_LISTENER_ACCESS Occurs while waiting for non-uniform memory access (NUMA) nodes to update state change. Access to state change is serialized.
SNI_TASK_COMPLETION Occurs when there is a wait for all tasks to finish during a NUMA node state change.
SOAP_READ Occurs while waiting for an HTTP network read to complete.
SOAP_WRITE Occurs while waiting for an HTTP network write to complete.
SOS_CALLBACK_REMOVAL Occurs while performing synchronization on a callback list in order to remove a callback. It is not expected for this counter to change after server initialization is completed.
SOS_DISPATCHER_MUTEX Occurs during internal synchronization of the dispatcher pool. This includes when the pool is being adjusted.
SOS_LOCALALLOCATORLIST Occurs during internal synchronization in the SQL Server memory manager.
SOS_MEMORY_USAGE_ADJUSTMENT Occurs when memory usage is being adjusted among pools.
SOS_OBJECT_STORE_DESTROY_MUTEX Occurs during internal synchronization in memory pools when destroying objects from the pool.
SOS_PHYS_PAGE_CACHE Accounts for the time a thread waits to acquire the mutex it must acquire before it allocates physical pages or before it returns those pages to the operating system. Waits on this type only appear if the instance of SQL Server uses AWE memory.,
SOS_PROCESS_AFFINITY_MUTEX Occurs during synchronizing of access to process affinity settings.
SOS_RESERVEDMEMBLOCKLIST Occurs during internal synchronization in the SQL Server memory manager.
SOS_SCHEDULER_YIELD Occurs when a task voluntarily yields the scheduler for other tasks to execute. During this wait the task is waiting for its quantum to be renewed.
SOS_SMALL_PAGE_ALLOC Occurs during the allocation and freeing of memory that is managed by some memory objects.
SOS_STACKSTORE_INIT_MUTEX Occurs during synchronization of internal store initialization.
SOS_SYNC_TASK_ENQUEUE_EVENT Occurs when a task is started in a synchronous manner. Most tasks in SQL Server are started in an asynchronous manner, in which control returns to the starter immediately after the task request has been placed on the work queue.
SOS_VIRTUALMEMORY_LOW Occurs when a memory allocation waits for a resource manager to free up virtual memory.
SOSHOST_EVENT Occurs when a hosted component, such as CLR, waits on a SQL Server event synchronization object.
SOSHOST_INTERNAL Occurs during synchronization of memory manager callbacks used by hosted components, such as CLR.
SOSHOST_MUTEX Occurs when a hosted component, such as CLR, waits on a SQL Server mutex synchronization object.
SOSHOST_RWLOCK Occurs when a hosted component, such as CLR, waits on a SQL Server reader-writer synchronization object.
SOSHOST_SEMAPHORE Occurs when a hosted component, such as CLR, waits on a SQL Server semaphore synchronization object.
SOSHOST_SLEEP Occurs when a hosted task sleeps while waiting for a generic event to occur. Hosted tasks are used by hosted components such as CLR.
SOSHOST_TRACELOCK Occurs during synchronization of access to trace streams.
SOSHOST_WAITFORDONE Occurs when a hosted component, such as CLR, waits for a task to complete.
SQLCLR_APPDOMAIN Occurs while CLR waits for an application domain to complete startup.
SQLCLR_ASSEMBLY Occurs while waiting for access to the loaded assembly list in the appdomain.
SQLCLR_DEADLOCK_DETECTION Occurs while CLR waits for deadlock detection to complete.
SQLCLR_QUANTUM_PUNISHMENT Occurs when a CLR task is throttled because it has exceeded its execution quantum. This throttling is done in order to reduce the effect of this resource-intensive task on other tasks.
SQLSORT_NORMMUTEX Occurs during internal synchronization, while initializing internal sorting structures.
SQLSORT_SORTMUTEX Occurs during internal synchronization, while initializing internal sorting structures.
SQLTRACE_BUFFER_FLUSH Occurs when a task is waiting for a background task to flush trace buffers to disk every four seconds.
SQLTRACE_FILE_BUFFER Occurs during synchronization on trace buffers during a file trace.,
SQLTRACE_SHUTDOWN Occurs while trace shutdown waits for outstanding trace events to complete.
SQLTRACE_WAIT_ENTRIES Occurs while a SQL Trace event queue waits for packets to arrive on the queue.
SRVPROC_SHUTDOWN Occurs while the shutdown process waits for internal resources to be released to shutdown cleanly.
TEMPOBJ Occurs when temporary object drops are synchronized. This wait is rare, and only occurs if a task has requested exclusive access for temp table drops.
THREADPOOL Occurs when a task is waiting for a worker to run on. This can indicate that the maximum worker setting is too low, or that batch executions are taking unusually long, thus reducing the number of workers available to satisfy other batches.
TIMEPRIV_TIMEPERIOD Occurs during internal synchronization of the Extended Events timer.
TRACEWRITE Occurs when the SQL Trace rowset trace provider waits for either a free buffer or a buffer with events to process.
TRAN_MARKLATCH_DT Occurs when waiting for a destroy mode latch on a transaction mark latch. Transaction mark latches are used for synchronization of commits with marked transactions.
TRAN_MARKLATCH_EX Occurs when waiting for an exclusive mode latch on a marked transaction. Transaction mark latches are used for synchronization of commits with marked transactions.
TRAN_MARKLATCH_KP Occurs when waiting for a keep mode latch on a marked transaction. Transaction mark latches are used for synchronization of commits with marked transactions.
TRAN_MARKLATCH_SH Occurs when waiting for a shared mode latch on a marked transaction. Transaction mark latches are used for synchronization of commits with marked transactions.
TRAN_MARKLATCH_UP Occurs when waiting for an update mode latch on a marked transaction. Transaction mark latches are used for synchronization of commits with marked transactions.
TRANSACTION_MUTEX Occurs during synchronization of access to a transaction by multiple batches.
UTIL_PAGE_ALLOC Occurs when transaction log scans wait for memory to be available during memory pressure.
VIA_ACCEPT Occurs when a Virtual Interface Adapter (VIA) provider connection is completed during startup.
VIEW_DEFINITION_MUTEX Occurs during synchronization on access to cached view definitions.
WAIT_FOR_RESULTS Occurs when waiting for a query notification to be triggered.
WAIT_ON_SYNC_STATISTICS_REFRESH Occurs when waiting for synchronous statistics update to complete before query compilation and execution can resume.
WAIT_XTP_CKPT_CLOSE Occurs when waiting for a checkpoint to complete.,
WAIT_XTP_CKPT_ENABLED Occurs when checkpointing is disabled, and waiting for checkpointing to be enabled.,
WAIT_XTP_CKPT_STATE_LOCK Occurs when synchronizing checking of checkpoint state.,
WAIT_XTP_GUEST Occurs when the database memory allocator needs to stop receiving low-memory notifications.,
WAIT_XTP_HOST_WAIT Occurs when waits are triggered by the database engine and implemented by the host.,
WAIT_XTP_OFFLINE_CKPT_LOG_IO Occurs when offline checkpoint is waiting for a log read IO to complete.,
WAIT_XTP_OFFLINE_CKPT_NEW_LOG Occurs when offline checkpoint is waiting for new log records to scan.,
WAIT_XTP_PROCEDURE_ENTRY Occurs when a drop procedure is waiting for all current executions of that procedure to complete.,
WAIT_XTP_RECOVERY Occurs when database recovery is waiting for recovery of memory-optimized objects to finish.,
WAIT_XTP_TASK_SHUTDOWN Occurs when waiting for an In-Memory OLTP thread to complete.,
WAIT_XTP_TRAN_DEPENDENCY Occurs when waiting for transaction dependencies.,
WAITFOR Occurs as a result of a WAITFOR Transact-SQL statement. The duration of the wait is determined by the parameters to the statement. This is a user-initiated wait.
WAITSTAT_MUTEX Occurs during synchronization of access to the collection of statistics used to populate sys.dm_os_wait_stats.
WORKTBL_DROP Occurs while pausing before retrying, after a failed worktable drop.
WRITE_COMPLETION Occurs when a write operation is in progress.
WRITELOG Occurs while waiting for a log flush to complete. Common operations that cause log flushes are checkpoints and transaction commits.
XACT_OWN_TRANSACTION Occurs while waiting to acquire ownership of a transaction.
XACT_RECLAIM_SESSION Occurs while waiting for the current owner of a session to release ownership of the session.
XACTLOCKINFO Occurs during synchronization of access to the list of locks for a transaction. In addition to the transaction itself, the list of locks is accessed by operations such as deadlock detection and lock migration during page splits.
XACTWORKSPACE_MUTEX Occurs during synchronization of defections from a transaction, as well as the number of database locks between enlist members of a transaction.
XE_BUFFERMGR_ALLPROCESSED_EVENT Occurs when Extended Events session buffers are flushed to targets. This wait occurs on a background thread.
XE_BUFFERMGR_FREEBUF_EVENT Occurs when either of the following conditions is true:
XE_DISPATCHER_CONFIG_SESSION_LIST Occurs when an Extended Events session that is using asynchronous targets is started or stopped. This wait indicates either of the following:
XE_DISPATCHER_JOIN Occurs when a background thread that is used for Extended Events sessions is terminating.
XE_DISPATCHER_WAIT Occurs when a background thread that is used for Extended Events sessions is waiting for event buffers to process.
XTPPROC_CACHE_ACCESS Occurs when for accessing all natively compiled stored procedure cache objects.,
XTPPROC_PARTITIONED_STACK_CREATE Occurs when allocating per-NUMA node natively compiled stored procedure cache structures (must be done single threaded) for a given procedure.,

Learn About DBAaaS

Hire Us

Help

Legal