>From JDBC Docs. http://java.sun.com/j2se/1.3/docs/api/index.html
"setTransactionIsolation:
Note: This method cannot be called while in the middle of a transaction."
Bill
> -----Original Message-----
> From: [EMAIL PROTECTED]
> [mailto:[EMAIL PROTECTED]]On Behalf Of marc
> fleury
> Sent: Wednesday, June 27, 2001 3:59 PM
> To: [EMAIL PROTECTED]
> Subject: RE: [JBoss-dev] CVS update:
> jboss/src/main/org/jboss/ejb/plugins/jaws/jdbc JDBCCommand.java
>
>
> |> Bill are you saying..
> |>
> |> BeanA BeanB
> |> / \ / \
> |> PoolA PoolB PoolC PoolD <--- configure here
> |> \ \ / /
> |> \ \ / /
> |> \ /
> |> \ /
> |> DB1
> |>
> |
> |Nope, I'm saying this
> |
> |
> |ReadCommittedPool
> |SerializedPool
>
> so just 2 pools per database existing, one per isolation level
>
> no duplication per bean?
>
> mmm at least its simpler than I thought... but again are we sure that we
> CANNOT change the isolation levels within one transaction?
>
> if (we can NOT change) 2 pools
> if (we can change) 1 pool
>
> |BeanA/jaws.xml
> |# You want BeanA to access DB with isolation level READ_COMMITTED
> |<datasource>ReadCommittedPool</datasource>
> |
> |BeanB/jaws.xml
> |# You want BeanA to access DB with isolation level SERIALIZED
> |<datasource>SerializedPool</datasource>
>
> sure it is simple, do you need 2 pools though?
>
> |> Am I correct in saying that the pool will not hand out a
> |> connection that is
> |> associated with a transaction? If so you only get connections that are
> |> clear and clean...
> |>
> |
> |Again, I'm pretty sure you're wrong here. The pools will hand
> out the same
> |connection that is already associated with the transaction you are in.
>
>
> which is what I meant, that the pool will not hand out a
> connection already
> in a transaction to another transaction. SO when you get a
> connection it is
> already and only associated to your transaction only. Setting your
> isolation level should be transparent to the driver it is a discussion you
> are having with the database (but I understand you are saying that setting
> different isolation levels WITHIN a transaction results in commit?).
>
>
> |I don't know, maybe it is as easy as
> |
> |jdbcExecute(...)
> |{
> |
> |JBossDataSource ds = (JBossDataSource)jawsEntity.getDataSource();
> |Connection con = ds.getConnectionWithIsolation(SERIALIZED);
> |
> |PreparedStatement stmt = con.createPreparedStatement(...)
> |yadayadayada
> |}
> |
> |But this change is practically the same as having 2 separately defined
> |pools.
>
> no no no I am saying
>
> jdbcExecute(..)
> {
> ds=getDataSource();
> ds.setIL(whatever);
> do work;
> }
>
> well you are stuck with this "I have to use the right pool from
> the get go"
> and my questions are more around the setting of isolation levels within a
> transaction. Regardless of the pool.
>
> since we all know that you get the same connection all the time that is
> good.
>
> |I will double check on this, but David Jencks has a real good
> |point. Unless
> |we're using real XA and 2pc, mixing isolation levels between beans to the
>
> hmmmm that's orthogonal (if I read that paragraph right), my thinking here
> (but I could be wrong on how the drivers do it) is that your driver only
> knows the transaction and registers with it to listen to the demarcation.
> It is the db that manages the isolation of the queries on
> individual records
> and it does so based on tags that you passed to it through the connection.
> That you set the isolation level at the beginning, statically, or that you
> set them within the transaction (ONE transaction) should not make a
> difference and certainly should NOT commit the transaction going on. But
> you seem to indicate that a connection in a given transaction
> cannot modify
> its isolation level to talk to different records it is static.
>
> Transaction A {
>
> uses connection 1
> setIL(readserialized)
> talks to "customer" records and that is readserialized,
> setIL(readcommited) <-- Driver will commit transaction A????
> talks to "debitcard" records and that is readcommited,
> }
> }
>
> the connection is a connection period, and you tell it wich IL to use for
> the next invocations. Obviously different ILs on the same record
> would throw
> exceptions but same IL on same records, even if you have many ILs because
> many records, within the same transaction.
>
> I guess I tend to think of the isolation as a record thing, not a
> transaction thing, even though we use the transaction to implement it
>
> marcf
>
>
>
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