How DB actually works when needs to update a table?
posted 11 years ago
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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