READ UNCOMMITTED or NOLOCK on Oracle

[ClaireHCM]

Hi,

In SQL Server, I can do

1. select * from tb_name (nolock)
or
2. SET TRANSACTION ISOLATION LEVEL
READ UNCOMMITTED

To avoid blocking due to lengthy select operation.

Do we have something like this in Oracle?

Thanks
Claire

 

[Thargy]

Claire,

no, but (irrelevantly speaking) you can SET TRANSACTION LEVEL ISOLATION SERIALIZABLE.

The reason for the no, is that Oracle by default provides a read-consistent view of data. The upshot of this design is that readers never block writers. Your question is moot, because it just is never a problem in Oracle.

Read-consistent views are in my opinion, one of Oracle's great strengths.

Regards

T

 

[karluk]

Thargtheslayer's answer is correct - Oracle doesn't support the "READ UNCOMMITTED" isolation level, but that's because it doesn't need it, not from a weakness in the product. Here is a link to a more detailed discussion of the available isolation levels within Oracle.

http://www.oracle.com/technology/oramag/oracle/05-nov/o65asktom.html