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How DB actually works when needs to update a table?
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Kamyar Onikzeh
Ranch Hand
Joined: Sep 10, 2003
Posts: 30
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Hi there.
I'm new to DB and have a quastion.
How actually DB2 or Oracle works when you run a transaction which contains
for example 10 updates?
which one is correct?
1- copies the rows going to be updated to a temp space -->
writes the updates directly to the main table -->
if Commit happens -- > it's OK! and forgets the temp space
if Rollback happens --> rewrites the temp space to the original table
2- inserts the updates to a temp space -->
if Commit happens --> replaces the old rows in the table with new ones
if Rollback happens --> nothing going to do with the original table and forgets about the temp space
could anyone please describe it with a refrence from IBM or Oracle
Thank you in advance.
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"The greatest pleasure in life is doing what people say you cannot do." --Walter Bagehot<p>SCJP 1.4<br />SCWCD 1.3
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Jeanne Boyarsky
internet detective
Marshal
Joined: May 26, 2003
Posts: 26173
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Kamyar,
No updates are written to the main table right away. They are written to a file called a "rollback log" first.
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subject: How DB actually works when needs to update a table?
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