Hi!
----- Original Message -----
From: "Mark Matthews" <[EMAIL PROTECTED]>
Newsgroups: mailing.database.mysql
Sent: Tuesday, October 08, 2002 5:07 AM
Subject: Re: transaction isolation level
> Jianliang Zhao wrote:
...
> >>I am connecting to MySql 3.23(innodb) with
> >>mysql-connector-java-2.0.14-bin.jar. I set the global transaction
> >>isolation level to READ COMMITTED. However, I still couldn't see the
> >>committed changes through JDBC client. Does anyone know about this
> >>issue?
...
> The isolation level of READ_COMMITTED has no effect currently in MySQL,
> unless you're using BDB tables...InnoDB runs either as REPEATABLE_READ
> or SERIALIZABLE, and converts everthing else to REPEATABLE_READ, because
> it can do REPATABLE_READ as fast (or faster) than most other DB's
> READ_COMMITTED.
I have to correct that BDB always runs at the SERIALIZABLE isolation level.
The default for InnoDB is REPEATABLE READ, and you can enhance it to
SERIALIZABLE with the
SET [GLOBAL | SESSION] TRANSACTION ISOLATION LEVEL
{ READ UNCOMMITTED | READ COMMITTED | REPEATABLE READ | SERIALIZABLE }
SQL command. Since MyISAM uses table locking, we can say that MyISAM always
runs at the SERIALIZABLE level.
The command SHOW VARIABLES currently shows the MySQL default isolation level
as READ-COMMITTED, but it has no effect on any of the table handlers.
Version 4.0.5 will probably feature a new InnoDB isolation level READ
COMMITTED. I will probably at the same time change the MySQL default
isolation level to REPEATABLE READ. You can then lower the InnoDB isolation
level by the command
SET [GLOBAL | SESSION] TRANSACTION ISOLATION LEVEL ...
Users porting from Oracle and other databases will find READ COMMITTED a
useful level.
> -Mark
Best regards,
Heikki Tuuri
Innobase Oy
---
InnoDB - transactions, row level locking, and foreign key support for MySQL
See http://www.innodb.com, download MySQL-Max from http://www.mysql.com
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