Performance issues after migration

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Performance issues after migration

ramana3327

SSCoach

Points: 19722
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March 19, 2023 at 3:25 am

#4162414
Hi all,
We installed SQL 2017 standard edition. Taken the 2008r2 server database backup and restored into new 2017 server. Didn’t change the compatibility level. Same memory allocated as 2008r2 and did the update stats but seeing performance issues.
- This topic was modified 2 years, 2 months ago by ramana3327.

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Jeff Moden SSC Guru Points: 1004589 More actions · Answer 1

Start with the "Key Configuration Options" in the following article. Every single thing there can make a pretty good difference.

https://glennsqlperformance.com/2020/08/20/preventing-sql-server-upgrade-performance-issues/

--Jeff Moden

RBAR is pronounced "ree-bar" and is a "Modenism" for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
________Stop thinking about what you want to do to a ROW... think, instead, of what you want to do to a COLUMN.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

ramana3327 SSCoach Points: 19722 More actions · Answer 2

Thanks Jeff. According to the link performance regression happens with LEGACY_CARDINALITY ESTIMATION, when changed the database comparability level from old version(100) to native/new version(140). Here we didn’t change the compatibility level so LEGACY_CARDINALITY ESTIMATION is off.