Impact of transaction isolation implementation differences between databases on applications

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Impact of transaction isolation implementation differences between databases on applications

sastry mln
Hi,
 
  In http://www.oracle.com/technology/oramag/oracle/05-nov/o65asktom.html, Tom Kyte  described the differences between Oracle and non-oracle databases regarding the implementation of isolation levels.
 
  Not sure which non-oracle database he was referring to. but he made a point that other dbs use "shared read lock" for consistent answers which has a side effect: "Readers of data will block writers of data"

  1) MySQL

  I donot know how isolation levels implemented in mysql ..
  I found this discussions - http://forums.mysql.com/read.php?97,75190,75584.
  Here the author gave an example of 2 concurrent transactions where one commits before the other. The results of the first are available in the second. I do not see anything wrong with that, may be I missed the point of the author.
 
  2) PostGreSQL
   http://www.postgresql.org/docs/8.1/interactive/transaction-iso.html
    I read, reread, but could not completely grasp this.  
    seems it's an esoteric topic for my level of expertise.

  My Question is, does ofbiz architecture ensure consistent isolation behavior across all/popular databses?
  Please advise if we need to think through this before choosing a database for our business needs


regards
Sastry


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Re: Impact of transaction isolation implementation differences between databases on applications

David E. Jones-2

The database is responsible for transaction isolation, ie it's not  
something that OFBiz does. There is configuration in OFBiz for the  
desired transaction isolation. For comments and recommendations,  
please see the entityengine.xml file where this is configured (just  
before the datasource section).

-David


On Jul 8, 2009, at 8:36 PM, sastry mln wrote:

> Hi,
>
>  In http://www.oracle.com/technology/oramag/oracle/05-nov/o65asktom.html 
> , Tom Kyte  described the differences between Oracle and non-oracle  
> databases regarding the implementation of isolation levels.
>
>  Not sure which non-oracle database he was referring to. but he made  
> a point that other dbs use "shared read lock" for consistent answers  
> which has a side effect: "Readers of data will block writers of data"
>
>  1) MySQL
>
>  I donot know how isolation levels implemented in mysql ..
>  I found this discussions - http://forums.mysql.com/read.php?97,75190,75584 
> .
>  Here the author gave an example of 2 concurrent transactions where  
> one commits before the other. The results of the first are available  
> in the second. I do not see anything wrong with that, may be I  
> missed the point of the author.
>
>  2) PostGreSQL
>   http://www.postgresql.org/docs/8.1/interactive/transaction-iso.html
>    I read, reread, but could not completely grasp this.
>    seems it's an esoteric topic for my level of expertise.
>
>  My Question is, does ofbiz architecture ensure consistent isolation  
> behavior across all/popular databses?
>  Please advise if we need to think through this before choosing a  
> database for our business needs
>
>
> regards
> Sastry
>
>