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Oracle Tips by Burleson |
Oracle Dataguard
Chapter 2 - Data Guard Architecture
Redo Log File
Redo log groups are reused in a circular method
in that when the current redo log file fills, the LGWR starts
writing to the next redo log file group. When all of the redo log
groups are filled, the LGWR starts reusing the redo log members.
Archived Redo Log File
An archived redo log file is a replica of an
online redo log file. When an online redo log file group fills, the
archiver process copies the online redo log file to archival
destinations.
Once the archiver process completes the
replication of the online redo log file to archival destinations,
the online redo log file is marked for reuse. The redo thread number
and log sequence number uniquely identify an archived redo log file.
In case of media recovery, archived redo log files can be used to
update the database files.
In a Data Guard environment, a RAC Grid
should be an archival destination. Remote archival to the standby
database is achieved by a combination of the archiver process on the
primary database and the remote file server process of the standby
database. The archived redo log file on the RAC Grid is
exactly the same as the archived redo file written to a local
archival destination.
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