Re: JDBC transaction isolation

From:
Lew <lewbloch@gmail.com>
Newsgroups:
comp.lang.java.programmer
Date:
Thu, 3 May 2012 17:15:46 -0700 (PDT)
Message-ID:
<24360777.22.1336090546668.JavaMail.geo-discussion-forums@pbfk7>
Richard Maher wrote:

Arne Vajh=F8j wrote ...

Almost all database have it at the SQL level:

http://dev.mysql.com/doc/refman/5.5/en/set-transaction.html
http://www.postgresql.org/docs/9.1/static/sql-set-transaction.html and=

 

http://www.postgresql.org/docs/9.1/static/transaction-iso.html
http://msdn.microsoft.com/en-us/library/ms173763.aspx
http://docs.oracle.com/cd/B10500_01/server.920/a96524/c21cnsis.htm


 
Is anyone else of the opinion that Oracle really does not support the
serializable isolation level? (At least not in the way that SQL Server, R=

db,

Are you referring to their database product or some other product, such as =
Java?

and I'm sure others do) That is, it doesn't prevent inserts to the other=

 

txn's result-set,touched-rows by locking but rather fudges some sort of=

 

snapshot/consistent-view of old data. (And even then with restrictions)=

 

Eg: - select count(*) from employees where dept_code=1;


They do support SERIALIZABLE isolation, and properly by all evidence:

<http://docs.oracle.com/cd/E11882_01/server.112/e26088/statements_10005.htm=
#SQLRF01705>
"ISOLATION LEVEL Clause

"Use the ISOLATION LEVEL clause to specify how transactions containing data=
base
modifications are handled.

"The SERIALIZABLE setting specifies serializable transaction isolation mode=
 as defined in the
SQL standard. If a serializable transaction contains data manipulation lang=
uage (DML) that
attempts to update any resource that may have been updated in a transaction=
 uncommitted at
the start of the serializable transaction, then the DML statement fails."

See also
<http://docs.oracle.com/cd/E11882_01/server.112/e25789/consist.htm#BABEAFAH=

There's nothing in the definition of SERIALIZABLE transactions that require=
s locking.
<http://en.wikipedia.org/wiki/Isolation_(database_systems)#Serializable>

So whatever anyone else's opinion, or yours, the facts seem to be that Orac=
le Database properly supports SERIALIZABLE transaction isolation. Why do yo=
u ask for opinion when facts are in evidence?

--
Lew

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