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This is mainly a performance improvement for tempdb contention. It can happen in user databases, but less often than tempdb.
SQL Server 2019 : Concurrent PFS updates
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(137.6, 40%, 23%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ES%3C/text%3E%3C/svg%3E)
sakuraime
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Anyone can give more idea on what's actually it is ?
https://learn.microsoft.com/en-us/sql/sql-server/what-s-new-in-sql-server-ver15?view=sql-server-ver15
SQL Server | Other
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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(67.2, 1%, 16%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ETP%3C/text%3E%3C/svg%3E)
Tom Phillips 17,771 Reputation points2021-07-23T16:12:14.237+00:00 -
sakuraime 2,341 Reputation points
2021-07-25T12:22:56.017+00:00 thanks. but what actually is doing behind it ?
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Erland Sommarskog 121.4K Reputation points MVP Volunteer Moderator2021-07-25T20:15:13.553+00:00 This session from Bob Ward does not cover this particular improvement as I recall, but it can be a good introduction if you want to learn about latches in SQL Server: https://www.youtube.com/watch?v=iZcClP85Tes&ucbcb=1
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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(211.20000000000002, 78%, 30%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ECZ%3C/text%3E%3C/svg%3E)
Cris Zhan-MSFT 6,661 Reputation points2021-07-26T08:36:06.893+00:00 Hi,
Please refer to the document - Diagnose and resolve latch contention on SQL Server. The following are some of the contents of this document.
What is SQL Server latch contention
https://learn.microsoft.com/en-us/sql/relational-databases/diagnose-resolve-latch-contention?view=sql-server-ver15#what-is-sql-server-latch-contentionLatch contention on page free space (PFS) pages
https://learn.microsoft.com/en-us/sql/relational-databases/diagnose-resolve-latch-contention?view=sql-server-ver15#latch-contention-on-page-free-space-pfs-pages-
sakuraime 2,341 Reputation points
2021-07-27T01:27:35.813+00:00 still a bit confuse on how SQL Server 2019 improve this ..
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Cris Zhan-MSFT 6,661 Reputation points
2021-07-27T02:05:26.497+00:00 Hi,
This improvement changes the way that concurrency is managed with PFS updates so that they can be updated under a shared latch, rather than an exclusive latch.
You may need to learn more about SQL Server latch.
If you need more detailed instructions, I haven't found some more helpful information for the time being. -
sakuraime 2,341 Reputation points
2021-07-27T10:35:52.027+00:00 maybe this feature is a top secret.
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Dan Guzman 9,401 Reputation points2021-07-27T11:10:33.457+00:00 maybe this feature is a top secret.
I'd also like to know the internals of how a shared latch can protect concurrent PFS updates but it seems these specific implementation details haven't yet been publicly disclosed. But this is only for my curiosity since it's not actionable information. All I really need to know is "it just runs faster" ;-)
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