Category: Wait Types

Service Broker has a cluster of internal waits around its startup, shutdown, and endpoint machinery that share one story, so this page covers them together: Are They a Problem? No. Every one of these is lifecycle or configuration machinery, active at startup, shutdown, endpoint state changes, and routing updates, and none has been a contention…

BROKER_EVENTHANDLER is recorded by the per-instance Service Broker primary event handler thread while it waits for something to handle: a Broker timeout event, or Service Broker starting up or shutting down. One thread, always present, almost always waiting. Its arithmetic gives it away: the cumulative wait time for this type runs roughly equal to the…

BPSORT is recorded when a thread participates in a batch-mode sort, the columnstore-adjacent sort implementation (batch mode required columnstore involvement before SQL Server 2019; since then batch mode on rowstore widened the audience). Threads cooperating on a batch sort synchronise through this wait. Some of it is the ordinary sound of batch-mode sorts running. Is…

BMPALLOCATION is a wait associated with allocating bitmap structures used by parallel query plans. Bitmap operators let SQL Server filter rows early during parallel hash joins: the build side produces a bitmap of qualifying keys, and probe-side rows that cannot match are discarded before they travel across exchange operators. Threads synchronising on the allocation of…

ASYNC_IO_COMPLETION means SQL Server issued asynchronous I/O against a data file and is waiting for it to complete. Unlike the PAGEIOLATCH_* family, which covers ordinary page reads into the buffer pool, this wait belongs to bulk file operations: the data-reading side of backups, checkpoint writes flushing dirty pages, restores laying data down, and similar large-scale…

ASYNC_DISKPOOL_LOCK is recorded when a thread synchronises with the worker threads that manage long-duration file operations: creating and deleting files, zero-initialising new file space, and encrypting files for Transparent Data Encryption. Those operations run through a pool of workers, and coordinating with that pool produces this wait. It travels with the file-heavy moments of a…