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The redo prefix and .log suffixes indicate that this is redo log information. The g1m1
and g1m2 character strings capture the group and member numbers. This convention
is only an example; it??™s best to set conventions that youfind meaningful and stick to
them.
Archived redo logs
Youmay be wondering how to avoid losing the critical information in the redo log
when Oracle cycles over a previously used redo log.
Figure 2-6. Cycling redo logs
redog1m1.log redog1m2.log
Group 1
redog2m1.log redog2m2.log
Seq# =1
Seq# =2
Seq# =3
redog3m1.log redog3m2.log
Seq# =4
Group 2
Group 3
Sequence number advances as logs fill and cycle
=
=
=
46 | Chapter 2: Oracle Architecture
There are actually two ways to address this. The first is quite simple: you don??™t avoid
losing the information and you suffer the consequences in the event of a failure. You
will lose the history stored in the redo file when it is overwritten. If a failure occurs
that damages the datafiles, youmu st restore the entire database to the point in time
when the last backup occurred.


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