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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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    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.  ...

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    SQL Server 2016 introduces two distinct changes in the AlwaysOn transport, compression design.   Improved compression algorithms Parallel compression of log block data   Compression can be performed faster, using less resource overhead and maintains compression ratios.   SQL Server 2016 also introduces parallel compression operations.  The following chart outlines the performance and resource gains...

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    The SQL Server 2016, AlwaysOn, log transport takes advantage of hardware based encryption to significantly improve scale and performance.   SQL Server 2016 development efforts continued focusing on the AlwaysOn log shipping transport.  Testing revealed that software based encryption, while fundamentally sound, could be improved using hardware based capabilities.   The exchange of information between...

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    SQL Server leverages a worker pool for the In-Memory Optimized Database capabilities.  Prior to SQL Server 2016, increasing the size of the pool required you to enable a startup trace flag.   SQL Server 2016 removed the trace flag and updated the design to dynamically adjust the size of the In-Memory Optimized Database worker pool...

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    SQL Server leverages MSDTC for distributed transactions (begin distributed transaction, remote proc trans, etc.)   Prior to SQL Server 2016 the MSDTC service must be running (started) prior to any SQL Server, DTC based transaction activity.   SQL Server 2016 enhances SQL distributed transaction capabilities leveraging MSDTC, On Demand startup.  The On Demand startup of MSDTC...