Concepts: how much writing on disk for a single update

(I use 10.2.0.5 but I think that this applies to any version)

After reading lots of documentation on Oracle I started to think how often Oracle 'written' for a single update statement.

The following is correct?

For an update statement:
(1) the original data are written in tables UNDO space
(2) this is protected by a write first to REDO log
(3) the new data is written to the table space
(4) this is also protected by an entry first in the redo log
(5) after that fills in the redo log, it is copied to an archived log
(6) at the time of the backup that Archives archiving log is also best once more

So for a single update, I count at least six entries of the same data?
It is probably what makes the robust Oracle.

user12204556 wrote:
(I use 10.2.0.5 but I think that this applies to any version)

After reading lots of documentation on Oracle I started to think how often Oracle 'written' for a single update statement.

The following is correct?

For an update statement:
(1) the original data are written in tables UNDO space

Yes

(2) this is protected by a write first to REDO log

Yes

(3) the new data is written to the table space

No, your data still haven't write (immediately) to datafiles (your tablespaces logically). When point of control (when manually to CHANGE the point of VERIFICATION SYSTEM, SWITCH of NEWSPAPER, when the buffer cache is full, STOP IMMEDIATELY in backup database tablespace mode) then your blocks of data will apply to data files.

(4) this is also protected by an entry first in the redo log

Yes

(5) after that fills in the redo log, it is copied to an archived log

YesIn ARCHIVELOG mode()

(6) at the time of the backup that Archives archiving log is also best once more

YES.

So for a single update, I count at least six entries of the same data?

These are not same data! This is the mechanism of oracle database. Cancel the information generated immediately and ensure uniformity reading (to restore). Redo information just, contain no information. It comes to redo change agent who used methods of recovery (media and instance) and finally your data updates do not immediately write data by DBWR because files there is reason of performance.

Tags: Database

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