The PAGEIOLATCH_EX wait type in SQL Server is used to synchronize access to BUF structures; excessive PAGEIOLATCH_EX waits may indicate disk subsystem problems. The most frequently occurring buffer latching situation is when serialization is required on a buffer page.

1. Tuning for SQL Server
PAGEIOLATCH_EX Wait Types
Confio Software
12/4/2013
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2. About SQL Server
PAGEIOLATHCH_EX Wait Types
• In SQL Server, a latch is a short-term lightweight
synchronization object
• Buffer latches including the PAGEIOLATCH_EX wait type
synchronize access to BUF structures and associated pages
in the SQL Server database
• Most frequently occurring buffer latching situation is when
serialization is required on a buffer page
– These buffer latches are not held for the complete period of the
transaction
• PAGEIO latches are a subset of BUF latches
– Used when the buffer and associated data page or the index
page is in the middle of an IO operation
• PAGEIOLATCH wait types are used for disk-to-memory
transfers
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3. PAGEIOLATCH_EX (exclusive mode
page IO latch request)
• When a SQL Server user needs a page that is
not in buffer cache:
– Database must first allocate a buffer page
– Then it puts an exclusive PAGEIOLATCH_EX latch
on the buffer while the page is transferred from
disk to cache
– During this operation, SQL Server puts a
PAGEIOLATCH_EX request on the buffer on behalf
of the user
– After the write to cache is complete, the
PAGEIOLATCH_EX latch is released
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4. Indication of problem with
PAGEIOLATCH_EX waits
• Excessive PAGEIOLATCH_EX waits occur when:
– Data is transferred from disk to memory for
update operations and these transfers take time
to complete
• Excessive PAGEIOLATCH_EX waits may
indicate:
– Disk contention
– Other disk subsystem bottlenecks
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