Databases Reference
In-Depth Information
You may transfer backups of database files and the archived redo logs in various ways:
•
Manually transfer backups from the target host to the host on which you are duplicating the
database by using identical directory paths. For example, if the backups are stored in /u01/
backup on the source host, move them to the /u01/backup directory on the destination host.
•
Manually transfer backups from the target host to the duplicate host using different directory
paths (to a different location on the host where you're creating the duplicate database). For
example, if the backups are in the /u01/backup directory on the source host, copy them to the
/u02/backup directory on the destination host. You must then update the source database
control file using the
catalog
(
catalog start with <directory>
) command so it's aware of
the new location of the backups. You must do this because RMAN checks the backup metadata
in the control file for the location of the backup files and archived redo logs. Of course, this
means that for the
catalog
command to work you must have the /u02/backup directory on
the source host as well!
•
Use a network file system (NFS), and ensure that the source and destination hosts can both
access the same NFS mount point.
Starting with the Oracle Database 11g release, RMAN offers an alternative method of duplicating databases,
without using any source database backups. This type of database duplication, performed directly over the network,
is called active database duplication. In this chapter, we show you how to perform database duplication using both
the older backup-based duplication method and the relatively new innovation in database duplication, which
performs database duplication over the network without using any backups.
When you're duplicating databases with RMAN, the source and the destination databases can be on the same
or different servers. To create a duplicate database, RMAN uses what's called an
auxiliary database instance.
An
auxiliary instance is the database associated with the duplicate database. RMAN uses target channels to perform the
work involved in active database duplication. For backup-based duplication, auxiliary channels perfom the work of
duplication instead.
For active database duplication, RMAN can use image copies or backup sets. The capability to perform active
database duplication using backup sets is a new feature introduced in Oracle Database 12c Release 1.
It's important to remember that the most recent point to which you can recover a duplicate database is the last
redo log file archived by the source database. This is so because the duplication process doesn't back up and apply the
source database online redo log files. Therefore, RMAN will always perform a database point-in-time recovery during
database duplication.
You can use RMAN to duplicate a database in any of the following ways:
•
Active duplication: duplicate the database files directly over the network
•
Backup-based duplication without a target connection: use the recovery catalog and duplicate
files from RMAN backup sets and image copies
•
Backup-based duplication with a target connection: use RMAN to create duplicate database
files from existing RMAN backup sets and image copies
•
Backup-based duplication without a target connection or a recovery catalog: RMAN uses
backup sets and copies stored in a directory designated by the parameter
BACKUP_LOCATION
Also in this chapter, we talk about using RMAN to move data with transportable tablespaces. Oracle's
transportable tablespaces feature lets you move large amounts of data much faster than a traditional export and
import of data. This is because the transportable tablespace operation requires that you copy just the data files that
belong to the tablepspace whose contents you want to transport and merely export and import the metadata relating
to the tablespace. The transportable tablespace feature is highly useful when archiving historical data, performing
tablespace point-in-time recovery, and exporting and importing large data warehouse table partitions. You can even
transport tablespaces across platforms, which means you can use this feature to migrate Oracle databases from one
platform to another or move data from data warehouses to data marts running on smaller platforms.
