undo management in sql server 200

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undo management in sql server 200

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Topic

pavan27
Starting Member

8 Posts

Posted - 2007-05-20 : 11:27:30

hai to every one,

i am pavan working as oracle dba. in oracle we have undo table space.
when we issue rollback oracle gets old image from undo tablespace.

in sql server where it gets from old image.

who performs instance crash recovery(which back ground is responsible for it)

in sql server we have logwriter, lazy writers(back ground processes)
what are the other processess.

and some doubts are

how insert query works
how update query works,
how select query works.

means i issue update statement. command successfully executed. late issue rollback, from where sql server gets old imege of the data

please send me any archetecture book /pdf/online link

thanks
kumar

pavan
Associate Oracle DBA

spirit1
Cybernetic Yak Master

11752 Posts

Posted - 2007-05-20 : 11:57:30

there is no such architecture in sql server.

sql server doesn't have an undo space.

if you completed a transaction the only way to get the previous data back is to restore
from database and transaction log backups.

_______________________________________________
Causing trouble since 1980
blog: http://weblogs.sqlteam.com/mladenp

harsh_athalye
Master Smack Fu Yak Hacker

5581 Posts

Posted - 2007-05-20 : 11:58:00

Read about Transaction Log Architecture in SQL Server help. It's your best source of information. Other than that, you can also read Mastering SQL server 2005 by Kalen Delaney to learn more about SQL Server internals.

Harsh Athalye
India.
"The IMPOSSIBLE is often UNTRIED"

Kristen
Test

22859 Posts

Posted - 2007-05-20 : 17:02:58

Basically if you do:

INSERT ...
or
UPDATE ...

then there is no rollback.

However, if you do

[red]BEGIN TRANSACTION
INSERT ...
or
UPDATE ...

then you can choose to COMMIT or ROLLBACK.

(There is also an implicit transaction mode where everything starts a transaction that you have to manually COMMIT. Kinda safety-net-mode!)

Other than that if you are running Recovery Model set to FULL (on a particular DATABASE) then you can restore it to a point-in-time. So you could, for example, restore to a new, temporary, database up to the point at which some "accident" happened, and then manually "rescue" the data from the Temporary database back into the Live database.

"please send me any archetecture book /pdf/online link"

With the SQL Server tools install you will get "Books Online" (referred to as BoL), that is a good resource for this type of question. Its also available online at the Microsoft website.

Kristen

pavan27
Starting Member

8 Posts

Posted - 2007-05-21 : 13:05:20

hai sir,

thanks for the information. i am very thankful to you of the information provided by team members.

regards,
pavan

pavan
Associate Oracle DBA

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