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SQL Server Books online defines the wait type WRITELOG as “Occurs while waiting for a log flush to complete. Common operations that cause log flushes are checkpoints and transaction commits. “
A checkpoint writes all SQL dirty pages , currently in the buffer, onto disk. Transaction commits m......
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SQL Server Books online defines the OLEDB wait stat type as “Occurs when SQL Server calls the SQL Server Native Client OLE DB Provider. This wait type is not used for synchronization. Instead, it indicates the duration of calls to the OLE DB provider”
Examples of where OLEDB wait type may occur is ......
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SQL Server Books online defines the TRACEWRITE sql wait stat type as “Occurs when
the SQL Trace rowset trace provider waits for either a free buffer or a buffer with
events to process”
The trace rowset provider drops events from the internal buffer, if it needs the......
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SQL Server Wait Stats analysis and Perfmon Counters recorded high ASYNC_IO_COMPLETION, IO_COMLETION and BACKUPIO on Production SQL Servers. At first, I thought just one server was underperforming. As more jobs starting delaying , it was obvious more than one server was experiencing a slowdown.
A ......
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SQL Server Books online defines BACKUPIO as “Occurs when a backup task is waiting for data, or is waiting for a buffer in which to store data. This type is not typical, except when a task is waiting for a tape mount.”
BACKUPIO is not specifically an disk IO wait measure. And should not......
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When analysing the full Query Response time, it is of value to break the cycle down into 3 stages. This will allow greater understanding of what is occurring and how to resolve any delays.
These three phases, will equal Total Time time taken for a query to respond.
CPU (Running) = When in Running ......
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SQL Server Books online defines SOS_SCHEDULER_YIELD as “Occurs when a task voluntarily yields the scheduler for other tasks to execute. During this wait the task is waiting for its quantum to be renewed “
What is happening when a SOS_SCHEDULER_YIELD is measured? The SQLOS worker has vol......
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SQL Server Books online defines LOGMGR as "Occurs when a task is waiting for any outstanding log I/Os to finish before shutting down the log while closing the database"
Depending on what other waits are occurring – this could indicate an IO bottleneck. For example, if ASYNCH_IO_COMPLETION, IO......
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SQL Server Books online defines IO_COMPLETION as “Occurs while waiting for I/O operations to complete. This wait type generally represents non-data page I/Os. Data page I/O completion waits appear as PAGEIOLATCH_* waits”
As with ASYNC_IO_COMPLETION it is a symptom of an IO bottleneck......
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SQL Server Books online defines Async_io_completion as “Occurs when a task is waiting for I/Os to finish “
Mainly a symptom of an IO bottleneck. Cross check by identifying other wait stat indicators such as: IO_COMPLETION, WRITELOG,PAGEIOLATCH_X. The appearance of at least one of these......
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