Setting isolation level with JDriver for Oracle/XA

Question

edocs (http://e-docs.bea.com/wls/docs70/oracle/trxjdbcx.html#1080746) states that,
if using jDriver for Oracle/XA you can not set the transaction isolation level
for a transaction and that 'Transactions use the transaction isolation level set
on the connection or the default transaction isolation level for the database'.
Does this mean that you shouldn't try to set it programatically (fair enough)
or that you can't set it in the weblogic deployment descriptor either? Also anybody
got any idea what the default is likely to be if you are using an Oracle 9iR2
database? Is this determined by some database setting?

Answer 1

IJ wrote:
edocs (http://e-docs.bea.com/wls/docs70/oracle/trxjdbcx.html#1080746) states that,
if using jDriver for Oracle/XA you can not set the transaction isolation level
for a transaction and that 'Transactions use the transaction isolation level set
on the connection or the default transaction isolation level for the database'.
Does this mean that you shouldn't try to set it programatically (fair enough)
or that you can't set it in the weblogic deployment descriptor either? Also anybody
got any idea what the default is likely to be if you are using an Oracle 9iR2
database? Is this determined by some database setting?The system should honor the setting defined in the deployment descriptor,
however, for oracle it may not be helpful to change it. Oracle provides two
isolation levels. The default is always READ_COMMITTED. The other
setting is SERIALIZABLE, but this hurts performance, and is also problematic
in the way oracle implements it. For instance, even if you set SERIALIZABLE,
oracle will not lock read data. It will allow other transactions to read and/or
alter data trhat another ongoing SERIALIZABLE transaction has read. The
only way to really lock read data in oracle is to issue oracle-specific SQL in
your select: "SELECT ..... FOR UPDATE".
All in all, you should collect a strong case for why you can't proceed with
READ_COMMITTED first. Then you should research oracle's recommendations
(and their problem record) with SERIALIZABLE.
Joe Weinstein at BEA