Compatibility Levels sql server 2012

  • I have compatibility levels 90 for few of the DB's and I want to bump it upto 110  since it is sql 2012 with sp4..for better performance.
    Can I rollback/reverse the changes if required?
    Does it require an restart to take effect?
    Can I update the settings on PROD anytime?
    Will it impact any application or user negatively?
    Thanks

  • sizal0234 - Tuesday, November 20, 2018 3:45 PM

    I have compatibility levels 90 for few of the DB's and I want to bump it upto 110  since it is sql 2012 with sp4..for better performance.
    Can I rollback/reverse the changes if required?
    Does it require an restart to take effect?
    Can I update the settings on PROD anytime?
    Will it impact any application or user negatively?
    Thanks

    What are you trying to fix, and why?
    Changing the compatibility level can be done at any time.  There is no re-start required. 
    However, I recommend testing thoroughly before you make these changes.  This may be set to 90 compatibility for a reason.

    Michael L John
    If you assassinate a DBA, would you pull a trigger?
    To properly post on a forum:
    http://www.sqlservercentral.com/articles/61537/

  • Thanks!
    I am trying to optimize the sql server and make changes which improves the performance. it is 2012 enterprise edition but has 90 lvls which I think is not the good option to be on.
    Having said that, what could be possible reasons for keeping it on older compatibility levels and do I have to approach application side or developer team ?

  • sizal0234 - Tuesday, November 20, 2018 4:12 PM

    Thanks!
    I am trying to optimize the sql server and make changes which improves the performance. it is 2012 enterprise edition but has 90 lvls which I think is not the good option to be on.
    Having said that, what could be possible reasons for keeping it on older compatibility levels and do I have to approach application side or developer team ?

    How can you optimize SQL when you are unsure of the effect your changes may have? 
    You have cleared the cache, which is not an optimization technique.  
    You have turned on auto update stats, which is normally a good thing, but there may be additional things that need to be done in regards to statistics.
    You have turned on the default trace, or at least have made sure it's on. Do you have a use for this?

    As far as compatibility levels, 90 is SQL 2005.   The internal changes that you may or may not be aware of may cause your code to break.  For example, the system tables changed  If any of your code is referring to the system, tables, it may break.
    Blindly changing the compatibility level without testing it first is not optimizing SQL.  You may actually be doing more damage than good. 

    In another post, I asked what problems you are trying to solve.  
    The answers, with as many details as possible, will help provide you the right information and set of suggestions to actually accomplish what you are trying to do.

    Michael L John
    If you assassinate a DBA, would you pull a trigger?
    To properly post on a forum:
    http://www.sqlservercentral.com/articles/61537/

  • Also, how do you fix a "slow database" when you don't know exactly what is slow? Do you have benchmarks? A list of the most used stored procedures?

  • pietlinden - Tuesday, November 20, 2018 4:51 PM

    Also, how do you fix a "slow database" when you don't know exactly what is slow? Do you have benchmarks? A list of the most used stored procedures?

    Same question.  
    What specific symptoms are you experiencing?  
    Is it the entire system, or parts of it?
    Can you provide some details on the following:
    Number of CPU's
    Amount of RAM
    Disk Configuration
    Size of databases
    Has maintenance been performed? Such as updating statistics.

    Michael L John
    If you assassinate a DBA, would you pull a trigger?
    To properly post on a forum:
    http://www.sqlservercentral.com/articles/61537/

  • Thank you..server has 4 processors, 64gb ram, approx 25gb 7 user dbs, 5 drives abcdef.

  • sizal0234 - Tuesday, November 20, 2018 5:30 PM

    Thank you..server has 4 processors, 64gb ram, approx 25gb 7 user dbs, 5 drives abcdef.

    What OS?  32 or 64?

    Can you run this, and post the results?

    sp_configure 'show advanced options', 1
    RECONFIGURE
    GO
    sp_configure
    GO

    Michael L John
    If you assassinate a DBA, would you pull a trigger?
    To properly post on a forum:
    http://www.sqlservercentral.com/articles/61537/

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