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This is the official team Web Log for Microsoft Customer Service and Support (CSS) SQL Support. Posts are provided by the CSS SQL Escalation Services team.
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      One of the best parts of my job is that I get to learn something new each and everyday.  This week I learned something completely new about deadlock monitor.  Deadlock monitor grants locks, yes you read that correctly. In a very small window the lock monitor prevents the releasing lock owner from directly granting...

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    The SOS_RWLock is a synchronization primitive used in various places throughout the SQL Server code base.  As the name implies the code can have multiple shared (readers) or single (writer) ownership.    Studying the SQL Server 2012 and 2014 implementation of the SOS_RWLock we found the core acquisition and wait list could be optimized.   SQL...

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    There are two(2) distinct checkpoint paths provided starting with SQL Server 2014, referred to as Automatic and Indirect.   The vast majority of documentation today highlights the behavior of automatic (classic) checkpoint.  This post outlines some historical aspects of checkpoint and provides the recommendation to leverage Indirect Checkpoint.   Before SQL Server 7.0 The database...

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    SQL Server uses WriteFileGather for the vast majority of data file write requests.   The logic is to consolidate dirty pages into a single I/O request.   For example page 1:13 and 1:12 are dirty resulting in a single WriteFileGather operation.       Is BUF[1] Dirty – Yes – Write with gather near Do hash...

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    SQL Server uses WriteFileGather for the vast majority of data file write requests.   The logic is to consolidate dirty pages into a single I/O request.   For example page 1:13 and 1:12 are dirty resulting in a single WriteFileGather operation.       Is BUF[1] Dirty – Yes – Write with gather near Do hash...

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      SQL Server 2016 introduces multiple log writer workers to the engine.    For many years the log device was limited by the capabilities of spinning media and hardware caches.    The advancement of hardware caches and fast storage types (SSD, flash, …) on large installations can saturate a single log write worker.   SQL Server 2016...

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    Recently I worked with a customer who noticed that several sessions[spid’s] in their SQL Server was acquiring ENCRYPTION_SCAN locks. So they got curious and started looking at this closer. Naturally, the first thing to check is presence of databases with Transparent Data Encryption [TDE] because encryption scan is the background process associated with TDE. Interestingly...

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    SQL Server’s Column Store feature is designed to accommodate large amounts of data and associated compression capabilities.  Microsoft studied numerous data layouts associated with column store and the CPU instructions required to process that data.   Various algorithms have been optimized throughout the column store code base.   A specific, SQL Server 2016  enhancement is the...

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    SQL Server 2016 enhanced the bulk insert activities (BULK INSERT), leveraging the CPUs vector instructions.   The vector based approach allows the bulk data to be processed faster.   For example, when inserting data from a text file the integer conversion leverages SSE instructions when the character length is more than 4 characters and trace flag...

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    The AlwaysOn log transport uses a SQL Broker based design to send and receive messages between the primary and secondary replicas.    Studying the transport behavior revealed various improvement opportunities.   Many of you have read the various materials indicating that log transportation between the primary and secondary is commonly 1/3 that of file copy speed.  ...