PAGEIOLATCH_NL is the Null (NL) mode member of the I/O page latch family, a placeholder so every latch mode has a PAGEIOLATCH_* counterpart. Null mode acquires nothing, and this wait type goes unused in practice.
Its siblings do the family’s real work: PAGEIOLATCH_SH for pages being read from disk, PAGEIOLATCH_EX and PAGEIOLATCH_UP for write-side I/O latching.
Is It a Problem?
No, and a non-zero value would itself be the anomaly. When I/O latching genuinely hurts, the evidence arrives through the working modes with high average durations, and the diagnosis runs through storage latency (sys.dm_io_virtual_file_stats), buffer pool health, and the queries driving reads.
Nothing about that investigation ever involves this placeholder.
Common Causes
- None; the mode is unused.
What To Do
- Nothing here. The
PAGEIOLATCH_SHdeep dive covers the family’s real diagnostics.
How To See It
Rank waits with Get-WaitStatistics; this entry stays at zero.
Part of the SQL Server Wait Types Library.
Related deep dive: PAGEIOLATCH_SH Wait Type.
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