Thank yout very much for your explanation:
This one time, at band camp, [EMAIL PROTECTED] said:
>I use the TransactionManager from the App Server via JNDI. The problem is
>that I need to do it in a context that I do not have a Transaction
running.
>I have tried to load the data in ReadOnly mode to see if JDO do not use
>transactions in such a mode of access, because there is no way of changing
>the data. However that was not the case. I supose that JDO uses
>transactions in all operations with the database. I wonder whether there
is
>a way of accessing using JDO with no transaction in progress only to
>extract a view of the data. There is no need to make a transaction because
>it is no use committing or rolling back a SELECT SQL.
>
>If that is not posible within JDO, must I create and destroy a transaction
>every time I need to make a report of what is up in the DataBase?,which
>implications does this random way of working have?, Could that make the
>performance of the access to the database worst or something like that?.
Raul,
Yes, Castor JDO requires transactions even if when performing a read-only
query.
The best explanation I can provide is an example, specifically, the dirty
read sceanario. A dirty read occurs where one transaction changes a value,
and a second transaction reads this value before the original change has
been committed or rolled back. If the first transaction is rolled back
then the data read in the second transaction is invalid or dirty. The
only way to guard against this and other phenomena is via transaction
isolation levels.
Bruce
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