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Oracle Tips by Burleson |
Oracle 10g RMAN Benefits of
Simplified Recovery Through Resetlogs
The Simplified Recovery Through Resetlogs feature
provides the following benefits:
-
There is no need to perform a full backup
after an incomplete recovery.
-
There is no need to recreate a new standby
database after a failover operation.
-
There is no need to change any backup
scripts, as there are no changes in the recovery commands to
take advantage of this functionality.
-
You can take incremental backups based on
full backups of a previous incarnation when you use RMAN.
-
Block media recovery can restore backups
from parent incarnation backups and recover the corrupted blocks
through a RESETLOGS operation.
How
does it work?
You may wonder how can you use the newly
generated logs with an earlier incarnation of the database. Oracle
10g introduces a new format specification for archived log files.
This new format avoids overwriting archived redo log files with the
same sequence number across incarnations.
SQL> show
parameter log_archive_format
NAME TYPE VALUE
----------------------- ----------- ----------------
log_archive_format string %t_%s_%r.dbf
The format specification is %r and represents
the resetlogs id. It is included in the default format for the
log_archive_format initialization
parameter. It will ensure that a unique name is constructed for the
archived redo log file during RMAN restore and SQL*plus auto
recovery mode.
During the RESETLOGS operation, the information
in v$log_history and v$offline_range records are no longer cleared.
In addition, two new columns have been added to indicate the
incarnation the records belong to: resetlogs_change# and
resetlogs_time.
Example:
SQL> select
recid, thread#, sequence#, resetlogs_change#,resetlogs_time
2 from v$log_history
3 where rownum < 20;
Get the complete Oracle10g story:
To get the code instantly, click here:
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