XE_LIVE_TARGET_TVF Wait Type in SQL Server

XE_LIVE_TARGET_TVF is recorded while a thread services a query that pulls data from an Extended Events live data stream, most commonly the “Watch Live Data” viewer in SSMS. The live target streams events to the watching client as they occur, and the serving thread accumulates this wait while that stream is open. It is a preemptive wait, so the thread stays busy from the scheduler’s point of view until the operation completes.

Simply put: someone, somewhere, has a live XEvents viewer open against this instance.

Is It a Problem?

Not as a contention point; it has not been observed causing trouble in its own right, and its size mostly tracks how long viewers stay open. It earns a look for two indirect reasons. First, it is a tell: unexpected live viewers on a production server mean someone is watching events, worth knowing during an incident review. Second, watching very high-frequency events live is not free, the event sessions themselves carry collection cost even though this wait is not where that cost shows.

Common Causes

• An SSMS “Watch Live Data” window open against an event session, often left running in a forgotten tab.
• Monitoring tools consuming XEvent live streams continuously.
• system_health or custom sessions being watched during troubleshooting.

What To Do

1. Identify live consumers: sys.dm_xe_sessions shows running sessions, and the live streaming target appears in sys.dm_xe_session_targets while a viewer is attached.
2. Close viewers that are no longer needed; the wait stops accumulating with them.
3. For continuous monitoring needs, prefer file targets read periodically over permanently attached live streams; same data, less standing machinery.
4. Review the event sessions being watched: if someone needed a live view of a high-frequency event, make sure the session’s filters are tight enough for production.

How To See It

Rank it against everything else with Get-WaitStatistics. Its presence is an inventory fact about live XEvent viewers rather than a performance signal.

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Part of the SQL Server Wait Types Library.
Related deep dive: ASYNC_NETWORK_IO Wait Type.