1)If the dynamic-update is very good then why default to false? Will it affect the performance?

2)"all" mean what?
3)"dirty" checking mean update the change column only is it? how about i already close the session and open again. Is it still work?
4)version property only usefull when i enable dynamic-update/insert is it? It is use to prevent lost update only?



Tutorial
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If you enable dynamic-update, you will have a choice of optimistic locking strategies:

version check the version/timestamp columns

all check all columns

dirty check the changed columns

none do not use optimistic locking

Dynamic update works within the session scope.

i.e., you do openSession(), either load the object or use select-before-update to the session and then set the attributes of the object with the new values. THe proxy recognizes the attributes that are dirty and can generate the sql for only those attributes.

However, this requires careful analysis of the problem at hand. If the session is open for too long, it locks the resources. Also, select-before-update will cause a database call before update.

Hope this helps.