Performing Oracle Advanced Recovery - OCP: Oracle Database 12c Administrator Certified Professional - page 309

As we have already mentioned, RMAN comes with a DUPLICATE DATABASE command.
Using the DUPLICATE DATABASE command provides a way to quickly move a database
between two different hosts that are running the same operating system. It also is a great
way to produce copies of existing databases on a different host, and it can also be used
to create standby databases on another host. Again, all of these need to be on the same
platform.
With active database duplication, the process is even easier because RMAN does not
need to access the database backup files of the database. Instead it simply scoops the data
from the database datafiles and duplicates them over the network to the new host. Again,
the same platform is required.
Note in these previous cases that the resulting database copy is logically a different data-
base, with a different database ID. So, while the data in the database might be the same, the
database itself is a logically different entity.
In Oracle Database 12 c RMAN introduced a feature called cross-platform transport-
able database. This provides the ability to transport the entire database and, in this case,
the resulting database is logically consistent with the source database. This is because along
with all the tablespaces that are moved over (as would occur with transportable tablespaces)
the SYSTEM tablespace is also moved over. This preserves the system related metadata such
as object_IDs and so on. This method of database movement does not provide for move-
ment across platforms with different byte formats.
Note that the cross-platform transport of databases can use image copies or RMAN
backup sets. Which one is more efficient will depend on a number of different factors,
such as CPU speed, memory availability, and network speed.
There are two different kinds of byte formats you will need to deal with as a DBA. These
are called endian byte formats. One is known as little endian and the other is known as big
endian. Until Oracle Database 12 c , the only way to move a complete database between plat-
forms with different byte formats was to use Oracle Data Pump to logically move the data
between the two platforms. This process could be complex and take much more time than
restoring an RMAN backup
RMAN now provides the ability to transport databases across the different byte formats.
A new command called CONVERT provides the ability to convert the files to the new byte
format on the target platform. You can convert the files on the source or destination server,
which allows you to control which machine is impacted by the conversion process.
The CONVERT process can be used with specific datafiles or tablespaces, or when moving
an entire database across platforms. Again, the use of image copies or RMAN backup sets
are both supported.
The problem with using RMAN in this case is that it will take time to move the data
between the source and destination hosts. This could impact the database performance and
network bandwidth. Also, you will have to take the source database offline for a while as
you synchronize the new database with the target database. The other problem is that the
move is almost an all-or-nothing type of decision. Rolling back the move, once you have
opened the database, can be time consuming and frustrating.
There are other solutions to moving databases to different hosts that reduce the down-
time and provide for testing before you actually open the new database up for users to use.
Let's look at those options for a moment.