Databases Reference
In-Depth Information
The
PARAMETER_VALUE_CONVERT
is used to avoid specifying each path related
parameter, this parameter doesn't define the
LOG_FILE_NAME_CONVERT
or
DB_FILE_
NAME_CONVERT
parameters.
Inter-platform database migration
When performing an inter-platform migration operation, due to natural OS
incompatibilities, the most commonly used method is a regular export/import
(exp/imp or the Data Pump version). This approach happens not to be a scalable
solution. The amount of data to transfer is directly proportional to the time taken
to complete. Day by day databases are growing larger and the maintenance
windows are becoming narrower, so a logical data transfer may leave us in a very
uncomfortable situation. If the database is 10g Release 1 or higher, the DBA can take
advantage of the inter-platform transportable tablespace feature. The total amount
of time it takes to have the database migrated to the target platform is equal to the
time it takes to prepare all tablespace metadata to be exported, plus the time it takes
to copy the datafiles to the target platform, plus the time to apply the inter-platform
datafile conversion, plus the time it takes to have the metadata imported.
The reason why a datafile belonging to a database created on HP-UX cannot be
read on a database created on a Windows x32 platform, or a datafile belonging to
a database on Linux cannot be read on Solaris is
Endianess
. Endianess is a term
used in computing and refers to the byte ordering used to represent data. This term
was coined after the Jonathan Swift's novel
The
Gulliver's
Travels
which depicts the
conflicts between Lilliput and Blefuscu who discussed which side was the right one
to crack the egg, the little end or the big end. Technically speaking, the big endian
format defines that the most significant byte is stored at the memory location with
the lowest address; the next byte value in significance is stored at the following
memory location and so on. On the other hand, the little endian format states that
the least significant byte value is at the lowest address, and the other bytes follow in
increasing order of significance.
The procedure to transport a tablespace across platforms is as follows:
1. Make the tablespace read only.
2.
Verify that you are working with a valid transportable set, that is
non self-contained tablespaces or tablespaces containing objects belonging
to SYS are not valid.
3.
Extract the metadata with the
transport_tablespace
option.
4.
Check out the source and target endian format, if those are compatible just
proceed, otherwise use RMAN to perform the endian conversion either at the
source or the target platform.
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