RE: Fav. Urban Legend...take two

You had to unleash that one on us.

-----Original Message-----
Sent: Thursday, March 14, 2002 12:57 PM
To: Multiple recipients of list ORACLE-L

Gotta be this one. I wouldn't love it so much except for the part about the USS Nimitz.

> When you place a tablespace in backup mode, the Oracle instance
> notes that a backup is being performed and internally compensates
> for it. As you know, it is impossible to make an authentic copy of a
> database file that is being written to. On receipt of the command to
> begin the backup, however, Oracle ceases to make direct changes to
> the database file. It uses a complex combination of rollback
> segments, buffers, redo logs, and archive logs to store the data
> until the end backup command is received and the database files are
> brought back in sync.
>
> Simplifying a hot backup in this way is tantamount to classifying
> the USS Nimitz as a boat. The complexity of the actions taken by the
> Oracle RDBMS under a hot backup could consume an entire chapter and
> is beyond the scope of this book. What you should understand is the
> trade-off for taking a hot backup is increased use of rollback
> segments, redo logs, archive logs, and internal buffer areas within
> the SGA.

--
Jeremiah Wilton
http://www.speakeasy.net/~jwilton

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-- 
Author: Post, Ethan
  INET: Ethan.Post_at_ps.net

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