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About an Oracle's Isolation Levels and lock mode [message #631497]

Wed, 14 January 2015 04:25

trybestpro
Messages: 17
Registered: September 2014
Location: HCM

Junior Member

Hi All,
I read document and know Oracle's Isolation Levels have the following categories: Read Uncommitted, Read Committed, Repeatable Read, Serializable.
Oracle's lock mode have the following categories (not all) : ROW SHARE (RS), ROW EXCLUSIVE (RX), SHARE (S), SHARE ROW EXCLUSIVE (SRX),
EXCLUSIVE (X).
But I don't understand what difference of Oracle's Isolation Levels and Oracle's lock mode ?

Thanks all.
Best regards.

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Re: About an Oracle's Isolation Levels and lock mode [message #631503 is a reply to message #631497]

Wed, 14 January 2015 04:55

Michel Cadot
Messages: 68732
Registered: March 2007
Location: Saint-Maur, France, https...

Senior Member
Account Moderator

There is no relation between locks and transaction isolation level.
By the way, Oracle does not know "Read Uncommitted" level.

See Database Concepts:
Chapter 9 Data Concurrency and Consistency
Chapter 10 Transactions

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Re: About an Oracle's Isolation Levels and lock mode [message #631507 is a reply to message #631503]

Wed, 14 January 2015 05:14

cookiemonster
Messages: 13963
Registered: September 2008
Location: Rainy Manchester

Senior Member

Isolation Levels determine what data you can see when you run a query.
Locks determine what data (and objects) you can modify.

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Re: About an Oracle's Isolation Levels and lock mode [message #631510 is a reply to message #631497]

Wed, 14 January 2015 05:29

John Watson
Messages: 8964
Registered: January 2010
Location: Global Village

Senior Member

Are you by any chance from a SQL Server or Sybase background? Those "databases" do have to apply locks to achieve certain levels of isolation because they can't provide read consistency any other way. Oracle isn't like that.

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Re: About an Oracle's Isolation Levels and lock mode [message #631513 is a reply to message #631503]

Wed, 14 January 2015 07:55

trybestpro
Messages: 17
Registered: September 2014
Location: HCM

Junior Member

Hi,

My question mean what Oracle's Isolation Levels used to do ? and what Oracle's lock mode used to do ?
I do not distinguish between the functions of the two things above.

Thanks.

[Updated on: Wed, 14 January 2015 07:58]

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Re: About an Oracle's Isolation Levels and lock mode [message #631514 is a reply to message #631513]

Wed, 14 January 2015 08:05

BlackSwan
Messages: 26766
Registered: January 2009
Location: SoCal

Senior Member

trybestpro wrote on Wed, 14 January 2015 05:55

Hi,

My question mean what Oracle's Isolation Levels used to do ? and what Oracle's lock mode used to do ?
I do not distinguish between the functions of the two things above.

Thanks.

which part of below do you NOT understand?

cookiemonster wrote on Wed, 14 January 2015 03:14

Isolation Levels determine what data you can see when you run a query.
Locks determine what data (and objects) you can modify.

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Re: About an Oracle's Isolation Levels and lock mode [message #631515 is a reply to message #631514]

Wed, 14 January 2015 08:08

trybestpro
Messages: 17
Registered: September 2014
Location: HCM

Junior Member

BlackSwan wrote on Wed, 14 January 2015 16:05

trybestpro wrote on Wed, 14 January 2015 05:55
Hi,

My question mean what Oracle's Isolation Levels used to do ? and what Oracle's lock mode used to do ?
I do not distinguish between the functions of the two things above.

Thanks.

which part of below do you NOT understand?

cookiemonster wrote on Wed, 14 January 2015 03:14
Isolation Levels determine what data you can see when you run a query.
Locks determine what data (and objects) you can modify.