Category: Wait Types

SQLTRACE_INCREMENTAL_FLUSH_SLEEP is recorded by a background thread sleeping between checks for SQL Trace data that needs flushing to a trace file. Because the default trace runs on practically every instance (it is the lightweight always-on trace that records events like file growths and DDL), this thread exists and sleeps everywhere, accumulating wait time around the…

TERMINATE_LISTENER is recorded when a thread waits for a SQL Server Network Interface (SNI) listener to be destroyed. SNI is the protocol layer wrapping TDS packets over whatever transports are configured (TCP, named pipes, shared memory), and listeners get torn down during instance shutdown, endpoint reconfiguration, and network setting changes. A teardown marker from the…

TRACE_EVTNOTIF is recorded when event notifications are configured, once per firing of an event that has a notification attached. Event notifications are the Service Broker-based mechanism that turns trace events and DDL events into messages on a queue, letting you react asynchronously to things happening in the engine. The wait’s volume therefore mirrors the firing…

TRACEWRITE is recorded by the SQL Trace rowset provider while it waits for a free trace buffer, or for a buffer containing events to hand to the consumer. The rowset provider is the path used when a client consumes trace events live, which in practice means SQL Server Profiler or an application reading a trace…

UCS_SESSION_REGISTRATION is recorded when a thread waits for access to the list of Service Broker sessions so it can add or remove one. The Unified Communications Stack (UCS) underlies Broker’s connection handling, and session registration passes through this small lock. Broker connection lifecycle bookkeeping, in a word. Is It a Problem? No; it has not…

VDI_CLIENT_OTHER is recorded by threads involved in copying database data through the Virtual Device Interface, most commonly automatic seeding of a new Availability Group replica, and in Azure whenever something triggers a database copy (service tier changes, geo-replication setup). The quirk that earns it a page: the system threads created for seeding, on the primary…

WAIT_ON_SYNC_STATISTICS_REFRESH is recorded when a query has to wait for a synchronous statistics update to finish before it can compile and run. With auto-update statistics in its default synchronous mode, a query that trips the staleness threshold on a table’s statistics stops, updates those statistics right there, and only then compiles. This wait, added so…

WAIT_XTP_CKPT_CLOSE is recorded when a thread waits for an In-Memory OLTP (XTP) checkpoint to complete. XTP checkpoints differ from disk-based ones: they continuously roll data into checkpoint file pairs, and a checkpoint “close” seals the current set. Threads coordinating with that close event park here. Present wherever memory-optimized filegroups exist, however lightly used. Is It…

WAIT_XTP_HOST_WAIT is recorded when a thread waits for an In-Memory OLTP operation that was initiated by the regular database engine and implemented by the XTP host layer, the bridge through which the traditional engine and the in-memory engine cooperate. Cross-engine housekeeping lands its wait time here. Another member of the XTP background family, present wherever…