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PAGEIOLATCH_SH

Short Description

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.

Detailed Description

Latches are lightweight, fast methods of managing concurrency on a specific resource.

The PAGEIOLATCH_* group of latches are seen in management of data pages.

PAGEIOLATCH_SH is waiting for a latch to be allocated in share (SH) mode so that a page can be read into memory and be available for other sessions to read.

How to reduce this wait

Whilst long waits on PAGEIOLATCH_* may indicate problems with the disk subsystem, it is important to check against a performance baseline to check:

  • Check for large increase in the volume of I/O
  • Check for large increases in database time
  • Check for large increases in the volume of queries
  • Check for changes in execution plans

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