Re: ISOLATION LEVEL

  • From: "Niall Litchfield" <niall.litchfield@xxxxxxxxx>
  • To: "Hemant K Chitale" <hkchital@xxxxxxxxxxxxxx>
  • Date: Tue, 10 Jul 2007 16:28:52 +0100

Thanks Hemant, and Alex F for pointing out that what I wrote was utter and
complete garbage, contradicted and corrected by my second reference. I don't
know what came over me. Sheesh!

From my second reference

Oracle Isolation Levels

Oracle provides these transaction isolation levels.
*Isolation Level* *Description*  Read committed This is the default
transaction isolation level. Each query executed by a transaction sees only
data that was committed before the query (not the transaction) began. An
Oracle query never reads dirty (uncommitted) data.

Because Oracle does not prevent other transactions from modifying the data
read by a query, that data can be changed by other transactions between two
executions of the query. Thus, a transaction that runs a given query twice
can experience both nonrepeatable read and phantoms.
Serializable Serializable transactions see only those changes that were
committed at the time the transaction began, plus those changes made by the
transaction itself through INSERT, UPDATE, and DELETE statements.
Serializable transactions do not experience nonrepeatable reads or phantoms.
Read-only Read-only transactions see only those changes that were committed
at the time the transaction began and do not allow INSERT, UPDATE, and
DELETE statements.

idiot boy!

--
Niall Litchfield
Oracle DBA
http://www.orawin.info

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